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Frontal section showing four earl stages of tooth development.

Frontal Section Showing Tooth Development

Frontal section showing four earl stages of tooth development.

The palate and alveolar arch.

Palate

The palate and alveolar arch.

The organs of mastication of the Sea Urchin. Mastication, or chewing, is the process by which food is crushed and ground by teeth.

Masticating Apparatus of Echinus Lividus

The organs of mastication of the Sea Urchin. Mastication, or chewing, is the process by which food is…

Labial view of temporary teeth of the left side.

Temporary Teeth

Labial view of temporary teeth of the left side.

Lingual view of temporary teeth.

Lingual View of Temporary Teeth

Lingual view of temporary teeth.

Permanent teeth, right side.

Permanent Teeth

Permanent teeth, right side.

Right half of upper jaw (from below), with the corresponding teeth. The letters and numbers point to the classes of teeth and the numbers in classes.

Upper Jaw with Teeth

Right half of upper jaw (from below), with the corresponding teeth. The letters and numbers point to…

Right half of lower jaw, with the corresponding teeth. The letters and numbers point to the various cusps or their modifications on the different teeth.

Lower Jaw with Teeth

Right half of lower jaw, with the corresponding teeth. The letters and numbers point to the various…

Vertical section of a molar tooth.

Vertical Section of a Molar

Vertical section of a molar tooth.

Vertical section of a tooth in situ. Labels: c, pulp cavity; 1, enamel with radial and concentric markings; 2, dentin with tubules and incremental lines; 3, cementum or crusta petrosa; 4, pericemental membrane; 5, bone of mandible.

Vertical Section of a Tooth

Vertical section of a tooth in situ. Labels: c, pulp cavity; 1, enamel with radial and concentric markings;…

Enamel prisms. A, Fragments and single fibers of the enamel isolated by the action of hydrochloric acid; B, Surface of a small fragment of enamel, showing the hexagonal ends of the fibers.

Enamel Prisms

Enamel prisms. A, Fragments and single fibers of the enamel isolated by the action of hydrochloric acid;…

An outer view of the right superior maxilla.

Outer View of Superior Maxilla

An outer view of the right superior maxilla.

The inner aspect of the right superior maxilla.

Inner Aspect of Superior Maxilla

The inner aspect of the right superior maxilla.

Ossification of superior maxilla. A, outer side. B, inner side. C, under side. Labels: a, nasal process; b, orbital plate; c, anterior nasal spine; d, infraorbital groove; e, infraorbital foramen; f, anterior palatine groove; g, palatal process; h, premaxillary suture; i, alveolar process.

Ossification of Superior Maxilla

Ossification of superior maxilla. A, outer side. B, inner side. C, under side. Labels: a, nasal process;…

Shown is a coronal section passing inferiorly through interval between between the first and second molar teeth. Labels: 1, groove of superior longitudinal sinus; 2,crest for attachment of falx cerebri; 3, crista galli of ethmoid; 4, cristiform plate of ethmoid; 5, perpendicular plate of ethmoid, assisting in the formation of nasal septum; 6, lateral mass of ethmoid consisting of the ethmoidal cells; 7, os planum of ethmoid; 8, middle meatus of nose; 9, middle turbinated bone; 10, opening from the middle meatus; 11, orbital plate of superior maxilla; 12, frontomalar suture; 13, infraorbital groove; 14, antrum or maxillary sinus; 15, canal for anterior dental nerve and vessels exposed; 16, inferior meatus of nose; 17, alveolar process of the superior maxilla; 18, nasal surface of inferior turbinated bone; 19, groove for anterior palatine nerve and vessels; 20, palatal process of superior maxilla; 21, maxillary crest forming part of nasal septum; 22, vomer forming part of nasal septum.

Coronal Section of Skull

Shown is a coronal section passing inferiorly through interval between between the first and second…

Archaeopteryx, sometimes referred to by its German name Urvogel ("original bird" or "first bird"), is the earliest and most primitive bird known. Archaeopteryx lived in the late Jurassic Period around 155–150 million years ago, in what is now southern Germany during a time when Europe was an archipelago of islands in a shallow warm tropical sea, much closer to the equator than it is now.

Archaeopteryx

Archaeopteryx, sometimes referred to by its German name Urvogel ("original bird" or "first bird"), is…

Coronal section through the closed mouth. The slit liked character of the vestibule, the manner which the tongue fills up the mouth cavity, the close apposition of the teeth, the relations of the roots of the upper molars to the antrum of Highmore, the plica sublingualis over the sublingual gland, and the position of the ranine artery should be noted.

Section Through Mouth

Coronal section through the closed mouth. The slit liked character of the vestibule, the manner which…

Open mouth showing palate and tonsils. It also shows the two palatine arches, and the pharyngeal isthmus through which the nasopharynx above communicates with the oral portion of the pharynx below.

Mouth Showing Palate and Tonsils

Open mouth showing palate and tonsils. It also shows the two palatine arches, and the pharyngeal isthmus…

Vertical section of canine tooth to illustrate the various parts and structures.

Structure of Canine Tooth

Vertical section of canine tooth to illustrate the various parts and structures.

The permanent teeth of the right side, outer or labial aspect. The upper row shows the upper teeth, the lower row the lower teeth. The wide vertical labial ridge is distinct on the upper canine and premolar teeth.

Permanent Teeth

The permanent teeth of the right side, outer or labial aspect. The upper row shows the upper teeth,…

The permanent teeth of the right side, inner of lingual aspect. The upper row shows the upper teeth, the lower row the lower teeth. The cingulum is distinct on the upper incisors and both canines, the lingual cusp on the upper lateral incisor and the upper canine.

Permanent Teeth

The permanent teeth of the right side, inner of lingual aspect. The upper row shows the upper teeth,…

The upper permanent teeth.

Upper Permanent Teeth

The upper permanent teeth.

The lower permanent teeth, viewed from above.

Lower Permanent Teeth

The lower permanent teeth, viewed from above.

Horizontal section through both the upper and lower jaws to show the roots of the teeth. The sections were carried through the bones a short distance from the edge of their alveolar borders. The upper figure shows the upper teeth, the lower figure the lower teeth. Note the flattened roots of the lower incisors, the two root canals in the anterior root of each lower molar, and the confluence of the three roots of the upper wisdom teeth.

Jaw Showing Roots of Teeth

Horizontal section through both the upper and lower jaws to show the roots of the teeth. The sections…

To show the relation of the upper to the lower teeth when the mouth is closed. The manner in which a tooth of one row usually strikes against two teeth of the opposite row, and the resulting interlocking of the teeth, is to be noted.

Teeth

To show the relation of the upper to the lower teeth when the mouth is closed. The manner in which a…

The temporary teeth of the left side. The masticating surfaces of the tow upper molars are shown above. In the second row the upper teeth are viewed from the outer or labial side. In the third row the lower teeth are shown in a similar manner; and below are the masticating surfaces of the two lower molars. In the specimen from which the first upper molar was drawn the two outer or buccal cusps were not distinctly separated, as is often the case.

Temporary Teeth

The temporary teeth of the left side. The masticating surfaces of the tow upper molars are shown above.…

Diagram to illustrate the development of a tooth. I. Shows the downgrowth of the dental lamina D.L. from the surface epithelium E and the beginning of the enamel germ E.G. II. Shows the further growth of the enamel germ and its invagination. III. The enamel germ is more invaginated, and its inner layer of cells becomes columnar. A, the dental lamina, grows thinner, but near its posterior or lingual edge there is an enlargement R.G which is the reserve germ for a permanent tooth. The superficial cells of the dentine papilla P are becoming columnar. IV. The inner columnar cells of the enamel germ ( called enamel cells) A have formed a cap of enamel EN, inside which the superficial cells of the papilla, the odontoblasts O, have formed a layer of dentine D. V. Shows a more advances stage still. The deposit of dentine is extending downwards, and enclosing the papilla to form the future pulp, in which a vessel V is seen. Labels: A, inner layer; B, outer layer; C, remains of intermediate cells; D, dentine; D.L, dental lamina; E, epithelium; E.G, enamel germ; EN, enamel; F, dental furrow; L.D, labio-dental furrow; M, connective tissue cells; O, odontoblasts; P, dentine papilla; R.G, reserve germ; V, blood vessels.

Development of a Tooth

Diagram to illustrate the development of a tooth. I. Shows the downgrowth of the dental lamina D.L.…

The scarifier is a instrument used for cultivating soil. "a, frame; b, handles; d, teeth; e, wheels; f, draft-hook." -Whitney, 1911

Scarifier

The scarifier is a instrument used for cultivating soil. "a, frame; b, handles; d, teeth; e, wheels;…

The skeleton of a horse. Axial Skeleton. The Skull. Cranial Bones: a, occipital, 1; b, wormian, 1; c, parietal, 2; d, frontal, 2; e, temporal, 2; sphenoid, 1; ethmoid, 1; auditory ossicles, 8. Facial bones: h, nasal, 2; g, lachrymal, 2; f, malar, 2; i, superior maxilla, 2; k, premaxila, 2; palatine, 2; pterygoid, 2; vomer, 1; tubinals, 4; l, inferior maxilla; 1; hyoid (segments), 5. Teeth: m, incisors, 12; n, canines, 4; o, molars, 24. The trunk: p-v, cervical vertebrae, 7; w, dorsal vertebrae, 18; x, lumbar vertebrae, 6; y, sacrum, 1; z, coccygeal vertebrae (variable), 18, d, d, ribs, 36; sternum (6-7 sternebrae), 7; *,coastal cartilages. Appendicular Skeleton. Pectoral Limb: e', scapula, 2; f', humerus, 2; g', radius, 2; h', ulna, 2. Carpus-i', trapesium, 2; k', cuneiform, 2; l', lunar, 2; m', scaphoid, 2; n', unciform, 2; o', magnum, 2; p', trapezoid, 2; q', pisiform, 2. Metacarpus-r', large bone, 2; s', small bone, 4. Digits- u', proximal phalanges, 2; v, median phalanges; w', distil phalanges, 2; t', large sesamoids, 4; small sesamoids, 2. Pelvic Limbs: Pelvis- b', ilium, 2; d' ischium, 2; c', pubis, 2. The limb- y', femur, 2; z', patella, 2; a', tibia, 2; b', fibula, 2. Tarsus- c', calcaneum, 2; d', astragalus, 2; e'. cuboid, 2; f', cuneiforme magnum, 2; g', cuneiforme medium, 2; h", cuneiforme parvum, 2. Metatarsus: large bone, 2; small bone, 4. Digit: proximal phalanges, 2; median phalanges, 2; distal phalanges, 2; large sesamoids, 4; small sesamoids, 2.

Skeleton of a Horse

The skeleton of a horse. Axial Skeleton. The Skull. Cranial Bones: a, occipital, 1; b, wormian, 1; c,…

The skeleton of a horse. Showing its relation to the contour of the animal, viewed laterally. Labels: A, temporal fossa; B, inferior maxilla; C, atlas; D, dentata; E, cervical vertebrae; F, dorsal vertebrae; G, lumbar vertebrae; H, sacral vertebrae; I, coccygeal vertebrae; J, scapula; K, humerus; L, radius; L, ulna; M, carpus; N, trapezium; O, metacarpus; P, b. os suffraginis; Q, c. sesamoids; R, d. os coronae; S, e. os pedis; T, ribs; U., ilum; V, femur; X, patella; Y, tibia; y., Fibula; Z, tarsus; a, metatarsus; f, ligamentum nuchae, funicular portion; f' lamellar portion; 1, zygoma; 2, orbital fossa; 3, nasal peak; 4, incisor teeth; 4', canine teeth; 5, molar teeth; 6, external humeral trochanter; 7, scapular fossae; 8, coracoid apophysis; 9, cartilage of prolongation; 10, deltoid ridge, and external tuberosity; 11, olecranon; 12, costal cartilage; 13, anterior iliac spine; 14, ischium; 15, trochanter major; 16, trochanter minor; 18, anterior tibial tuberosity; 19, calcaneum; 20, small metacarpal and metatarsal or splint bones.

Skeleton of a Horse

The skeleton of a horse. Showing its relation to the contour of the animal, viewed laterally. Labels:…

Inferior aspect of horse's skull, the mandible being removed. Above the line A is the posterior region or base between A and B the middle, and below B the anterior or nasal region. Labels: a, occipital condyle; B, foramen magnum; c, styloid process; d, temporal articular surface; e, basioccipital bone; f, basispenoid bone; i, temporal articular surface; k, condyloid foramen; k', condyloid notch; l, foramen lacerum basis cranii; m, pterygoid foramen; n, palatine suture; o, palatine foramen; p, molar teeth; q, incisive opening; r, foramen incisivum.

Inferior Aspect of Horse Skull

Inferior aspect of horse's skull, the mandible being removed. Above the line A is the posterior region…

Lateral aspect of horse's skull. Labels: 1, occipital bone; 2, parietal bone; 3, frontal bone; 9, nasal bone; 11, nasal peak; 10, premaxilla; 8, superior maxilla; 6, lachrymal bone; 7, malar bone; 5, zygomatic process of the squamosal bone; 4, petrosal bone; e, its external meatus; 12, inferior maxilla; h, coronoid process f inferior maxilla occupying the temporal fossa; k, temporomaxillary articulation; l, molar teeth.

Lateral Aspect of Horse Skull

Lateral aspect of horse's skull. Labels: 1, occipital bone; 2, parietal bone; 3, frontal bone; 9, nasal…

The skeleton of an ox. Axial Skeleton. The skull. Cranial Bones- occipital, 1: b, parietal, 2; a, frontal, 2; c, temporal, 2; sphenoid, 1; ethmoid, 1; auditory ossicles, 8. Facial Bones- h, nasal, 2; e, lachrymal, 2; d, malar, 2; f, maxilla, 2; g, premaxilla, 1; i, inferior maxilla, 2; palatine, 2; pterygoid, 2; vomer, 1; turbinals, 4; hyoid series, 7. Teeth: incisors, 6; canines, 2; molars, 24. The trunk- k, cervical vertebrae, 7; l, dorsal vertebrae, 13; m, lumbar vertebrae, 6; n, sacrum ( five segments), 1; o, coccygal vertebrae (variable), 20; p, ribs, 26; * sternum (seven sternebrae), 1. Appendicular skeleton. Pectoral limb. t, scapula, 2; u, humerus, 2; v, radius, 2; w, ulna, 2. Carpus- x, trapezium, 2; y, cuneiform, 2; z, lunar; a', scaphoid, 2; b', unciform, 2; c', magnum, 2. Metacarpus: d', large bone, 2; e', small bone, 4; f', large sesamoids, 8. Digit- g', proximal phalanges, 4; h', median phalages, 4; i', distal phalanges, 4; k', small sesamoids, 4. Pelvic Limb. Pelvis- q, ilium, 2; s, ischium, 2; r, pubis, 2. The limb- l', femur, 2; m', patella, 2; n', tibia, 2. Tarsus-o', maleolar, 2; p', calcaneum, 2; q', astragalus, 2; r', cubocuneiform, 2; s', cuneiforme medium, 2; t', cuneiforme parvum, 2. Metatarsus: large bone, 2; u', small bone, 2. Large sesamoids, 8. Digit: proximal phalanges, 4; median phalanges, 4; distal phalanges, 4; small sesamoids, 4. Visceral skeleton. Bones of the heart, 2. The separate bones of the ruminant skeleton, as here considered are 251.

Ox Skeleton

The skeleton of an ox. Axial Skeleton. The skull. Cranial Bones- occipital, 1: b, parietal, 2; a, frontal,…

Skeleton of the hog. Axial skeleton. The skull. Cranial bones- a, occipital, 1; b, parietal, 2; d, frontal, 2; c, temporal, 2; sphenoid, 1; ethmoid, 1; auditory ossicles, 8. Facial Bones- g, nasal, 2; h, os rostri, 1; f, lachrymal, 2; e, malar, 2; i, maxilla, 2; k, premaxilla, 2; l, inferior maxilla, 1; palatine, 2; 2, pterygoid, 2; vomer, 1; turbinals, 4; hyoid series, 5. Teeth: incisors, 12; canines, 4; molars, 28. The trunk- m, cervicle vertebre (variable), 18; r, ribs, 28; * sternum (seven sternebrae), 1. Appendicular Skeleton. Pectoral Limb. v, scapula, 2; w, humerus, 2; x, radius, 2; y, ulna, 2. carpus: z, trapezium, 2; a', cuneiform, 2; b', lunar, 2; c', scaphoid, 2; d', unciform, 2; e', magnum, 2; f', trapezoid, 2; g', pisiform, phalanges, 8; l', distal phalanges, 8; l", small sesamoids, 8. Pelvic Limb. Pelvis: s, ilium, 2; t, pubis, 2; u, ischium, 2. The limb-m', femur, 2; n', patella, 2; o', tibia, 2; p' fibula, 2. Tarsus- q' calcaneum, 3; r', astragalus, 2; s', cuboid, 2; t', cuneiforme magnum, 2; u', ecto-cuneiforme, 2; v' w', meso and endo cuneiformes, 4. Metatatarsus: large bones, 8; x', small bones 2; y', large sesamoids, 16. Digit: proximal phalanges, 8; median phalanges, 8; distal phalanges, 8; small sesamoids, 8. Visceral Skeleton- None. The separate bones of the skeleton of the hog, as here considered, are 234.

Skeleton of a Hog

Skeleton of the hog. Axial skeleton. The skull. Cranial bones- a, occipital, 1; b, parietal, 2; d, frontal,…

The skeleton of the dog. Axial skeleton. The skull. Cranial bones- a, occipital, 1; b, parietal, 2; d, frontal, 2; c, temporal, 2; sphenoid, 1; ethmoid, 2; auditory ossicles, 8. Facial Bones- f, nasal, 2; e, lachrymal, 2; d, malar, 2; h, maxilla, 2; g, premaxilla, 2. Teeth: incisors, 12; canines, 4; molars, 26. The trunk- l, cervical vertebrae, 7; m, dorsal vertebrea, 13; n, lumbar vertebrae, 7; o, sacrum (three segments), 1; p, coccygeal phalanges (variable), 20; t, ribs, 26; * sternum (eight sternebrae), 1. Appendicular Skeleton. Pectoral Limb. u, scapula, 2; v, humerus, 2; w, radius, 2; x, ulna. Carpus: y, trapezium, 2; z cuneiform, 2; a', scaphoid, 2; b', unciform, 2; c', magnum, 2; d', trapezoid, 2; e', pisiform,2; metacarpal bones, 10; h', anterior sesamoids, 10; g' posterior sesamoids, 20. Digits- i' proximal phalanges, 10; k', median phalanges, 8; l', distal phalanges, 10; small sesamoids wanting. Pelvic Limb. Pelvis: q, ilium, 2; r, pubis, 2; s, ischium, 2. The limb-m', femur, 2; o', fabellae, 4; n', patella, 2; q', tibia, 2; p', tibial sesamoid, 2; r', fibula, 2. Tarsus: s', calcaneum, 2; t', astragalus, 2; u', cuboid, 2; v', superior cuneiform, 2; w', ectocuneiforme, 2; x', mesocuneiforme, 2; y', edocuneiforme, 2. Metatarsus: large bones, 8; z',small bones, 2; anterior sesamoids, 8; posterior sesamoids, 16. Digit: proximal phalanges, 8; median phalanges, 8; distal phalanges, 8; small sesamoids wanting. Visceral Skeleton. Os Penis, 1; Rudimentary clavicle (inconstant), 2. The bones of the Carnivora Skeleton, thus considered, are 345.

Skeleton of a Dog

The skeleton of the dog. Axial skeleton. The skull. Cranial bones- a, occipital, 1; b, parietal, 2;…

Tetraodontidae is a family of primarily marine and estuarine fish. The family includes many familiar species which are variously called puffers, balloonfish, blowfish, bubblefish, globefish, swellfish, toadfish, and toadies. They are morphologically similar to the closely related porcupinefish, which have large conspicuous spines (unlike the small, almost sandpaper-like spines of Tetraodontidae). The scientific name, Tetraodontidae, refers to the four large teeth, fused into an upper and lower plate, which are used for crushing the shells of crustaceans and mollusks, and red worms, their natural prey. Puffer Fish are the second most poisonous vertebrate in the world, the first being a Golden Poison Frog. The skin and certain internal organs of many Tetraodontidae are highly toxic to humans, but nevertheless the meat of some species is considered a delicacy in both Japan (as fugu) and Korea (as bok-uh). If one is caught while fishing, it is recommended that thick gloves are worn to avoid poisoning and getting bitten when removing the hook.

Blowfish

Tetraodontidae is a family of primarily marine and estuarine fish. The family includes many familiar…

Incisor and canine teeth of a horse. A, front, B, lateral, and C, corner incisor; D, canine teeth.

Incisor and Canine Horse Teeth

Incisor and canine teeth of a horse. A, front, B, lateral, and C, corner incisor; D, canine teeth.

Incisor tooth of a horse-posterior view. Labels: a, outer layer of enamel; b, inner layer of enamel round the infundibulum; c, dental star; d, the dentine.

Horse Incisor Tooth

Incisor tooth of a horse-posterior view. Labels: a, outer layer of enamel; b, inner layer of enamel…

The deadbeat has a second face on the pallets, called the 'locking' face, with a curved surface concentric with the pivot that the anchor turns on. When an escape wheel tooth is resting against one of these faces, its force is directed through the pivot axis, so it gives no impulse to the pendulum, allowing it to swing freely. During most of the pendulum's swing, the tooth is in this locked position. Near the bottom of the pendulum's swing the tooth slides off the locking face onto the slanted 'impulse' face of the pallet, allowing the escape wheel to turn and give the pendulum a push, before dropping off the pallet. The drag of the escape tooth on the locking face does add a small amount of friction to the pendulum's swing (this is called a frictional rest type escapement), but it is usually negligible. In contrast to the backward slant of the anchor escape wheel teeth, the deadbeat escape wheel teeth usually slant forward to ensure that the tooth makes contact with the locking face of the pallet, preventing recoil.

Deadbeat Escapement

The deadbeat has a second face on the pallets, called the 'locking' face, with a curved surface concentric…

The Saw-Toothed Grain Beetle (Oryzaephilus surinamensis) is a beetle of the Silvanidae family and is named after the saw teeth on the sides of its prothorax.

Saw-Toothed Grain Beetle

The Saw-Toothed Grain Beetle (Oryzaephilus surinamensis) is a beetle of the Silvanidae family and is…

Cartilaginous framework of the nostril-seen from above. Labels: a, right alar cartilage; a', left alar cartilage' b, terminal portion of the septum nasi.

Nostriils of a Horse

Cartilaginous framework of the nostril-seen from above. Labels: a, right alar cartilage; a', left alar…

Skull of a hog- showing healthy teeth.

Skull of a Hog

Skull of a hog- showing healthy teeth.

The teeth of a lion.

Teeth of a Lion

The teeth of a lion.

Stomach of a dog-inflated. Labels: a, cardiac portion; b, pyloric portion; c, esophageal orifice; d, duodenum.

Stomach of a Dog

Stomach of a dog-inflated. Labels: a, cardiac portion; b, pyloric portion; c, esophageal orifice; d,…

Lateral half of mandible of a rabbi, opened to show the arrangement of rodent teeth.

Mandible of a Rabbit

Lateral half of mandible of a rabbi, opened to show the arrangement of rodent teeth.

Alimentary canal of a bird. Labels: a, ingluvies; b, proventriculus; c, pancreas; d, duodenum; e, liver; f, biliary cyst and duct; g, pancreatic duct; h, intestice; i, the to caeca; k, rectum; l, right ureter; m, oviduct; n, its aperture in cloaca; o, opening of cloaca.

Alimentary Canal of a Bird

Alimentary canal of a bird. Labels: a, ingluvies; b, proventriculus; c, pancreas; d, duodenum; e, liver;…

"In wood-working, a saw in which the cutting-teeth are placed at the ends of radial arms instead of upon he rim of a disk." -Whitney, 1911

Rift Saw

"In wood-working, a saw in which the cutting-teeth are placed at the ends of radial arms instead of…

The Gules Ordinary is four wolf's teeth in argent (silver), moving from the sinister (left) side.

Gules Ordinary

The Gules Ordinary is four wolf's teeth in argent (silver), moving from the sinister (left) side.

"In railroad construction and canal- or road-work, a large scooping bucket armed with teeth and used with a steam-shovel or operated by power by means of chains that drag the bucket over or through loose material, causing it to scoop up a load." -Whitney, 1911

Shovel Bucket

"In railroad construction and canal- or road-work, a large scooping bucket armed with teeth and used…

The wels catfish is a scaleless fresh and brackish water catfish recognizable by its broad, flat head and wide mouth. The mouth contains lines of numerous small teeth, two long barbels on the upper jaw and four shorter barbels on the lower jaw. It has a long anal fin that extends to the caudal fin, and a small sharp dorsal fin positioned relatively far forward. It uses its sharp pectoral fins to capture prey. With these fins, it creates an eddy to disorient its victim, which it then simply engulfs in its enormous throat. It has very slippery green-brown skin. Its belly is pale yellow or white. Wels catfish can live for at least thirty years and have very good hearing.

Wels Catfish

The wels catfish is a scaleless fresh and brackish water catfish recognizable by its broad, flat head…

"Diagram of an Echinus (stripped of its spines). a, mouth; a', gullet; b, teeth; c, lips; d, alveoli; e, falces; f, f, auriculariae; g, retractor, and h, protractor, muscles of Aristotle's lantern; i, madreporic canal; k, circular ambulacral vessel; l, Polian pedicels; r, r, spines; s, tubercle; s', tubercle to which a spine is articulated; t, t, pedicellariae; u, anus; v, madreporic tubercle; x, ocular spot." -Whitney, 1911

Sea Urchin Section

"Diagram of an Echinus (stripped of its spines). a, mouth; a', gullet; b, teeth; c, lips; d, alveoli;…

An illustration of the valerian seed with attached pappus. In a composite flower, Pappus is the part of individual disk and ray flowers that surrounds the base, in the same manner as the calyx does in a non-compound flower. The pappus may be like bristles or tiny hairs, teeth, or scales, and is usually too small to see without magnification. Valerian is a hardy perennial flowering plant, with heads of sweetly scented pink or white flowers. The flowers are in bloom in the northern hemisphere from June to September. Valerian was used as a perfume in the sixteenth century.

Valerian Seed with Pappus

An illustration of the valerian seed with attached pappus. In a composite flower, Pappus is the part…

"Endless screw, a mechanical arrangement consisting of a screw the thread of which gears into a wheel with skew teeth, the obliquity corresponding to the angle of pitch of the screw." -Whitney, 1911

Endless Screw and Wheel

"Endless screw, a mechanical arrangement consisting of a screw the thread of which gears into a wheel…

"Epicycloidal teeth, teeth for gearing cut in the form of an epicycloid." -Whitney, 1911

Epicycloidal Teeth

"Epicycloidal teeth, teeth for gearing cut in the form of an epicycloid." -Whitney, 1911

"Equisetum sylvaticum: a, a, sheath crowned with teeth; b, branches; c, c, fruiting spikes. 2. Clypeola, bearing sporangia. 3. Spore, with elaters coiled about it." -Whitney, 1911

Wood Horsetail

"Equisetum sylvaticum: a, a, sheath crowned with teeth; b, branches; c, c, fruiting spikes. 2. Clypeola,…

"Hesperornis regalis, (a fossilized restoration) which stood about three feet high, had blunt teeth in the grooves of both maxilla and mandible, the number being thirty or more below, but considerably less above, where they did not reach to the exterior extremity. The bill was long and pointed, the rami of the lower jaw being entirely separate; the head was rather small, the neck long, and the quadrate bone articulated with the skull by one knob only. The sternum was long, broad, and flat, without keel; the furcula was decidedly reduced, the metatarsus, being little more than a humerus; the tail was fairly long and broad, but had no pygostyle." A. H. Evans, 1900

The Restoration of the Hesperornis Regalis

"Hesperornis regalis, (a fossilized restoration) which stood about three feet high, had blunt teeth…

"Ichthyornis victor and I. dispar, ...were small forms of about the size of a Partridge, with the habits and appearance, it is presumed, of Terns or Gulls. The head was extremely large in proportion to the remainder of the skeleton; the beak was long and pointed, with entirely separate rami to the mandible; the sharp teeth, fixed regularly in distinct sockets, were inclined backwards, and occupied the whole of the lower and at least the posterior half of the upper jaw; the keel of the sternum was large and broad; the dorsal and cervico-dorsal vertebrae were biconcave. the quadrate articulated to the skull by one knob,... the metatarsus was short and the whole foot small; a furcula was probably present; the wings were well developed, indicating great powers of flight; while the tail was comparatively short, and ended in a pygostyle." A. H. Evans, 1900

Skeleton Head of a Ichthyornis

"Ichthyornis victor and I. dispar, ...were small forms of about the size of a Partridge, with the habits…

Wild Oat Grass (Danthonia spicata), also referred to as White Top grass, and Old Fog grass, is common in dry, sunny pastures, with a stem one foot high, slender with short leaves. Narrow sheaths, bearded. The panicle is simple and there are seven flowered spikelets. The lower palea broadly ovate, loosely hairy on the back, longer than its awl-shaped teeth. Perennial and flowers in June.

Wild Oat Grass

Wild Oat Grass (Danthonia spicata), also referred to as White Top grass, and Old Fog grass, is common…

Wild Oat Grass (Danthonia spicata), also referred to as White Top grass, and Old Fog grass, is common in dry, sunny pastures, with a stem one foot high, slender with short leaves. Narrow sheaths, bearded. The panicle is simple and there are seven flowered spikelets. The lower palea broadly ovate, loosely hairy on the back, longer than its awl-shaped teeth. Perennial and flowers in June. Shown is a magnified spikelet.

Wild Oat Grass

Wild Oat Grass (Danthonia spicata), also referred to as White Top grass, and Old Fog grass, is common…

Wild Oat Grass (Danthonia spicata), also referred to as White Top grass, and Old Fog grass, is common in dry, sunny pastures, with a stem one foot high, slender with short leaves. Narrow sheaths, bearded. The panicle is simple and there are seven flowered spikelets. The lower palea broadly ovate, loosely hairy on the back, longer than its awl-shaped teeth. Perennial and flowers in June. Shown is a magnified spikelet. Shown is the upper pale.

Wild Oat Grass

Wild Oat Grass (Danthonia spicata), also referred to as White Top grass, and Old Fog grass, is common…