Fig. 276.—Development of Coecum: A, showing the gradual formation of septa; a, apex; ap, aperture; ss, first septum; s´s´, second septum. (After de Folin.) B, adult form of C. eburneum Ad., Panama, x 10.
Fam. 36. Chenopodidae (= Aporrhaidae).—Foot flat; lateral and marginal teeth not denticulate; shell resembling that of Strombus, outer lip dilated, wing-like, no labial sinus. Jurassic ——. Genera: Chenopus (= Aporrhais, Diastema, Malaptera, Harpagodes, Alaria) (last four from Secondary strata).
Fam. 37. Struthiolariidae.—Radula allied to that of Strombus, marginals occasionally multiplied; shell buccinoid, very solid, outer lip thickened, canal short, operculum claw-shaped, notched, nucleus terminal. Tertiary ——. Single genus, Struthiolaria (subg., Perissodonta, marginal teeth multiplied).
Fam. 38. Cypraeidae.—Mantle with two large lateral lobes reflected and meeting over the shell, siphon small; central and lateral teeth bluntly tricuspid or multicuspid, laterals fairly broad, edges cusped or finely pectinate; shell polished, solid, spire generally concealed in the adult or overlaid with enamel, aperture straight, narrow, nearly as long as the shell, toothed at the sides, channelled at each end, labium inflected; no operculum. Jurassic ——. Genera: Ovula (including Amphiperas, Transovula, Cyphoma, Radius, Simnia), Pedicularia, Cypraea (with subg., Cypraeovula, Cypraedia, and Trivia), and Erato.
Fam. 39. Doliidae.—Foot expanded, wider and longer than the shell, truncated and thickened in front, siphon very long and narrow; central tooth with very strong median and small lateral and basal cusps, lateral and marginals bluntly falciform; shell ventricose, without varices, spire short, outer lip generally simple, anterior canal rather wide, no operculum. Cretaceous ——. Genera: Dolium (subg., Malea, outer lip thickened, denticulate, reflected); Pirula, mantle with two lateral lobes reflected over part of the shell, shell fig-shaped (Fig. [278]).
Fig. 277.—Three stages in the growth of Pteroceras rugosum Sowb., E. Indies, showing the development of the ‘fingers.’
Fam. 40. Cassididae.—Foot broad, siphon long (radula, Fig. [125], p. 223); shell ventricose, with varices, spire short, outer lip reflected or thickened, anterior canal short, recurved narrow; operculum semi-lunar, with ribs radiating from a marginal nucleus. Cretaceous ——. Genera: Cassis (subg., Semicassis and Cypraecassis), Morio (= Cassidaria), Oniscia.
Fam. 41. Columbellinidae.—Shell solid, ribbed, usually cancellated, with an oblique posterior canal, columella callous, more or less reflected. Genera: Columbellina, Columbellaria, Zittelia, Petersia, Alariopsis (?). Secondary strata only.