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"Diagrammatic vertical section through disc and base of one of the arms of Antedon rosacea. The section is inter-radial on the left, radial on the right. t., Ciliated openings in body wall; h., sub-epithelial ambulacral nerve; l., water-vascular canal; k., tentacle; r., mouth; s., intestine; g., central plexus, with "chambered organ" at its base; f., coelom; R1.-R3., radial plates; Br., brachial plates; u., muscle; a., axial nerve-cord; d., central capsule; C.D., centro-dorsal plate; p., cirri; e., nerve branches from central capsule to cirri." -Thomson, 1916

A. Rosacea Arm

"Diagrammatic vertical section through disc and base of one of the arms of Antedon rosacea. The section…

"Ambulacral system of a starfish. a, ampullae; ap, Polian vesicles; c, circular canal; m, madreporite; m', madreporic canal; p, tube-feet; r, radial vessels; r', branches to ampullae." -Parker, 1900

Ambulacral System

"Ambulacral system of a starfish. a, ampullae; ap, Polian vesicles; c, circular canal; m, madreporite;…

"The anchor-shaped calcareous spicules which are attached to and protrude from the flat perforated calcareous plates in the integument of echinoderms of the genus."-Whitney, 1902

Ancora

"The anchor-shaped calcareous spicules which are attached to and protrude from the flat perforated calcareous…

The arms of the brittlestar are more flexible than those of the starfish. They move by lateral movements of the arms, and are much quicker than the typical starfish.

Brittlestar

The arms of the brittlestar are more flexible than those of the starfish. They move by lateral movements…

Crinoids are Echinoderms. They are distinguished by the fact that they are fixed, during the whole or a portion of the life of the animal, to submarine objects by means of a jointed flexible stalk or column.

Crinoid

Crinoids are Echinoderms. They are distinguished by the fact that they are fixed, during the whole or…

Crinoids are Echinoderms. They are distinguished by the fact that they are fixed, during the whole or a portion of the life of the animal, to submarine objects by means of a jointed flexible stalk or column.

Crinoid

Crinoids are Echinoderms. They are distinguished by the fact that they are fixed, during the whole or…

The echinoderm, the crinoid or feather-star.

Crinoid

The echinoderm, the crinoid or feather-star.

A sea cucumber may be compared t a sea urchin that has been drawn out in the direction of the pole - that is, from mouth to anus (Colton, 1903).

Sea Cucumber

A sea cucumber may be compared t a sea urchin that has been drawn out in the direction of the pole -…

"Dissection of Holothurian (Holothuria tubulosa) from the ventral surface." t, tentacles; tf, scattered tube-feet; c, calcareous ring; a, ampullae of tentacles; r, circular vessel; st, stone canal; o, Polian vesicle; rc, radial canals; lm, longitudinal muscles; g1-g2, gut; m, mesentery; cl, cloaca; an, anus; rt, right respiratory tree; ov, ovary. -Thomson, 1916

Holothurian Dissection

"Dissection of Holothurian (Holothuria tubulosa) from the ventral surface." t, tentacles; tf, scattered…

The spines are removed from most of the surface of this sand dollar.

Sand Dollar

The spines are removed from most of the surface of this sand dollar.

"Encrinite: head and piece of stem. Any fossil crinoid; a stone-lily: a term especially applied to the ordinary stalked form with a cylindrical stem and well-formed arms." -Whitney, 1911

Encrinite

"Encrinite: head and piece of stem. Any fossil crinoid; a stone-lily: a term especially applied to the…

"Encrinite: Any fossil crinoid; a stone-lily: a term especially applied to the ordinary stalked form with a cylindrical stem and well-formed arms. a, a, parts of the stem; b, b, separate joints." -Whitney, 1911

Encrinite

"Encrinite: Any fossil crinoid; a stone-lily: a term especially applied to the ordinary stalked form…

An ancient crinoid, sea lilies are flowerlike, with branching arms surrounding the central mouth.

Sea Lily

An ancient crinoid, sea lilies are flowerlike, with branching arms surrounding the central mouth.

An ancient crinoid, stone lilies are flowerlike, with branching arms surrounding the central mouth.

Stone Lily

An ancient crinoid, stone lilies are flowerlike, with branching arms surrounding the central mouth.

"Modes of forming mesoderm. A and B, special mesoblasts distinguishable early in egmentation (annelid): A, surface view from active pole; B, sectional view of same. ec, micromeres destined to form ectoderm; en, macromeres destined to form entoderm; m, primitive mesoblast which produces the mesoderm. C, amaeboid mesodermal cells (c) budding from entoderm into the segmentation cavity (s.c.), in an Echinoderm. a, archenteron." — Galloway

Mesoderm

"Modes of forming mesoderm. A and B, special mesoblasts distinguishable early in egmentation (annelid):…

"Ventral surface of disc of an Ophiuroid (Ophiothrix fragilis). g., Openings of genital pockets or bursae; m., mouth; v., ventral plates of arms; sp., spines of arms; tf., tube-feet--at the right side these are represented as retracted; o., the opening through which they are protruded; p., plates around mouth bearing the so-called teeth; one of these plates is perforated, and functions as the madreporite." -Thomson, 1916

Ophiuroid

"Ventral surface of disc of an Ophiuroid (Ophiothrix fragilis). g., Openings of genital pockets or bursae;…

Sea cucumber dissected to show alimentary canal.

Sea cucumber

Sea cucumber dissected to show alimentary canal.

A sea lily or crinoidea.

Sea Lily

A sea lily or crinoidea.

The Spiny Sea Star (Echinaster sentus) is an echinoderm in the Asteroidea class of starfish.

Spiny Sea Star

The Spiny Sea Star (Echinaster sentus) is an echinoderm in the Asteroidea class of starfish.

Sea-cucumbers are Echinoderms. They are worm-like in form. They move about by the alternate contraction and extension of their bodies.

Sea-cucumber

Sea-cucumbers are Echinoderms. They are worm-like in form. They move about by the alternate contraction…

Sea-stars are Echinoderms. The order Ophiuroides is closely related to starfishes. The arms of sea stars however, differ from those of starfishes in not containing any prolongations from the stomach.

Sea-star

Sea-stars are Echinoderms. The order Ophiuroides is closely related to starfishes. The arms of sea stars…

Sea-urchins are Echinoderms. Their shell is mainly composed of calcareous plates.

Sea-urchin

Sea-urchins are Echinoderms. Their shell is mainly composed of calcareous plates.

"Spicules of Holothurians. The series 1-6 shows stages in the development of an anchor and a plate in a Synapta. The series A-E shows stages in the development of a wheel in Chiridota, a synaptid." -Thomson, 1916

Holothurian Spicules

"Spicules of Holothurians. The series 1-6 shows stages in the development of an anchor and a plate in…

The common starfish is a five rayed star. The central body is called the disk and the arms are the rays.

Starfish

The common starfish is a five rayed star. The central body is called the disk and the arms are the rays.

The common starfish is a five rayed star. The central body is called the disk and the arms are the rays. This is the water tube system of the starfish.

Starfish

The common starfish is a five rayed star. The central body is called the disk and the arms are the rays.…

An echinoderm called a starfish or sea star.

Starfish

An echinoderm called a starfish or sea star.

"Starfish. I. Ventral surface; t.f., tube-feet extended; a.g., the ambulacral groove with the tube-feet retracted; m., the mouth. II. Dorsal surface, showing the position of the madrepore (M.); the two adjacent arms form the bivium." -Thomson, 1916

Starfish

"Starfish. I. Ventral surface; t.f., tube-feet extended; a.g., the ambulacral groove with the tube-feet…

"Diagrammatic cross-section of starfish arm. n., Radial nerve; b.v., radial blood vessel according to Ludwig, septum in pseud-haemal vessel according to others; w.v., radial water vessel; am., ampulla; t.f., tube-foot; p.c., a pyloric caecum cut across; s.p., a calcareous spine; g., a skin-gill; lac., spaces in the wall; go., ova in ovary; a.o., ambulacral ossicle." -Thomson, 1916

Starfish Arm

"Diagrammatic cross-section of starfish arm. n., Radial nerve; b.v., radial blood vessel according to…

"Apical disc of sea-urchin. In the centre is the periproct bearing the anus; around it are five genital or inter-radial plates (g.), one of which is modified as the madreporite (m.); beyond these five ocular or radial plates (o.); i.r.a., an inter-radial or inter-ambulacral area, with spines only; r.a., a radial or ambulacral area, with spines and openings for tube-feet." -Thomson, 1916

Sea Urchin

"Apical disc of sea-urchin. In the centre is the periproct bearing the anus; around it are five genital…

A fossil of Echinothuria floris, a species of sea urchin "having the plates of the shell overlapping or movably connected by soft parts." -Whitney, 1911

Urchin Fossil

A fossil of Echinothuria floris, a species of sea urchin "having the plates of the shell overlapping…

Sea urchin: the heavy projections are the spines; the long, slender ones are the tube feet.

Sea Urchin

Sea urchin: the heavy projections are the spines; the long, slender ones are the tube feet.

Phormosoma luculentum is a species of Sea Urchin in the class Echinoidea.

Sea Urchin

Phormosoma luculentum is a species of Sea Urchin in the class Echinoidea.