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"The skull of a cod. b, branchiostegal rays born on c.h., the ceratohyal bone; d, dentary portion of the mandible; f, frontal; h.m., hyomandibular; i.o., interoperculum; l, lachrymal; m, maxilla; n, nasal; o, operculum; p.m., premaxilla; p.o., preoperculum; p.s., parasphenoid; q, quadrate; s.o., sub-operculum; s.oc., supra-occipital." — Galloway

Cod Skull

"The skull of a cod. b, branchiostegal rays born on c.h., the ceratohyal bone; d, dentary portion of…

"Portion of a similar embryo at a later stage of growth. The praegenital somite, VII PrG, is still present, but has lost its rudimentary appendages; go, the genital operculum, left half; KM, the left pecten; abp4 to abp7, the rudimentary appendages of the lung-sacs." — The Encyclopedia Britannica, 1910

Embryo

"Portion of a similar embryo at a later stage of growth. The praegenital somite, VII PrG, is still present,…

This illustration shows the structure of capsule of Funaria: 5, capsule with calyptra, 5A, removed. 6, section of nearly mature capsule-sp, spore-forming cells surrounded on outside by loosely arranged chlorophyll-bearing cells; o, operculum; r, annulus; p, peristome; a, apophysis. 8, magnified view of a portion of the capsule, showing the annulus, r, and the thick-walled cells of the peristome, p, which are attached at their base to the epidermis by a double row of cells; sp, spore-forming cells, the doted line should run to the four roundish cells at the left. 7, the cells shown in 8, p, have split apart, thus orming the inner and outer teeth-like segments of the peristome.

Funaria

This illustration shows the structure of capsule of Funaria: 5, capsule with calyptra, 5A, removed.…

An illustration of the operculum of the maclurites, an extinct genus of snails.

Operculum of Maclurites

An illustration of the operculum of the maclurites, an extinct genus of snails.

"The first three pairs of mesosomatic appendages of Scorpio and Limulus compared. VII. The genital operculum; VIII. The pectens of Scorpio and the first branchial plate of Limulus; IX. The first pair of lung-books of Scorpio and the second branchial plate of Limulus. gp, Genital pore; epst, Epistigmatic sclerite; stg, Stigma or orifice of the hollow tendons of the branchial plates of Limulus." — The Encyclopedia Britannica, 1910

Mesosomatic

"The first three pairs of mesosomatic appendages of Scorpio and Limulus compared. VII. The genital operculum;…

"Diagrams of the meta-sternite st, with genital operculum op, and the first lamelligerous pair of appendages ga, with uniting sternal element st of Scorpio (left) and Limulus (right)." — The Encyclopedia Britannica, 1910

Meta-sternite

"Diagrams of the meta-sternite st, with genital operculum op, and the first lamelligerous pair of appendages…

"Hair-cap moss (Polytrichum commune). A, male plant; B, same, proliferating; C, female plant, bearing sporogonium; D, same; g, gametophyte; s, seta; c, capsule; o, operculum; a, calyptra, E, top view of male plant." -Gager, 1916

Hair-Cap Moss

"Hair-cap moss (Polytrichum commune). A, male plant; B, same, proliferating; C, female plant, bearing…

"Ventral view of a restoration of Palaeophonus Hunteri, Pocock, the Silurian scorpion from Lesmahagow, Scotland. Restored by R. I. Peacock. The meeting of the coxae of all the prosomatic limbs in front of the pentagonal sternum; the space for a genital operculum; the pair of pectens, and the absence of any evidence of pulmonary stigmata are noticeable in this specimen." — The Encyclopedia Britannica, 1910

Palaeophonus Hunteri

"Ventral view of a restoration of Palaeophonus Hunteri, Pocock, the Silurian scorpion from Lesmahagow,…