Fam. 4. Naricidae.—Tentacles broad in the middle, with sessile eyes at the exterior base, propodium narrow, quadrangular, a large epipodial veil on each side of the foot; shell naticoid, cancellated, with velvety periostracum. Jurassic——. Single genus: Narica.
Fam. 5. Xenophoridae.—Foot divided by a groove, anterior portion the larger; central tooth heart-shaped, with blunt cusps, lateral large, roughly triangular, marginals long, falciform; shell trochiform, somewhat flattened, attaching various fragments externally. Devonian——. Single genus, Xenophora (Figs. [25], [26], p. 64).
Fam. 6. Capulidae.—Ctenidium deeply and finely pectinate, visceral sac scarcely spiral, penis long, behind the right tentacle; shell roughly patelliform, with scarcely any spire, interior polished, usually with a septum or internal plate of variable form, no operculum. Devonian——. Principal genera (Fig. [155], p. 248); Capulus, shell cap-shaped, no internal plate; Platyceras (Palaeozoic, see p. [76]), Diaphorostoma (Palaeozoic), Addisonia (?); Crucibulum, internal appendage funnel-shaped; Crepidula (including Crepipatella and Ergaea), shell slipper-shaped, with a large septum; Calyptraea (including Galerus and Trochita), internal lamina semi-spiral.
Fam. 7. Hipponycidae.—Foot aborted, animal sedentary, adductor-muscle shaped like a horse’s hoof, fastened on the ventral side to the region of attachment, or to a thin calcareous plate which closes the aperture like a valve; ventral side of the body surrounded by a mantle with papillose border, which corresponds morphologically to the epipodia, head emerging between the dorsal and ventral mantles. Shell thick, bluntly conical, surface rugose. Eocene ——. Genera: Hipponyx; Mitrularia, a narrow half funnel-shaped appendage within the shell.
Fig. 272.—Two specimens of Crepidula (marked a and b) on an old shell of Murex radix Gmel.
Fam. 8. Solariidae.—Foot large, eyes sessile, near the outer base of the tentacles, radula abnormal (p. [224]); shell more or less depressed, lip simple, umbilicus wide, margins often crenulated, operculum variable. The proper position of the family is quite uncertain. Ordovician——. (i.) Solariinae. Genera: Solarium, shell depressed, highly finished, angular at periphery, operculum corneous, central tooth absent, laterals and marginals numerous, long, and narrow; Platyschisma (Silurian). (ii.) Toriniinae. Genera: Torinia, whorls usually rounded, operculum (Fig. [183]) conically elevated, spiral externally, central tooth present, marginals few, edge pectinated; Omalaxis. (iii.) Euomphalinae, shell planorbiform, whorls rounded. Genera: Euomphalus, Ophileta, Schizostoma, Eccyliomphalus (all Palaeozoic).
Fam. 9. Homalogyridae.—Tentacles absent, eyes sessile, central tooth unicuspid on a quadrangular base, laterals and marginals replaced by an oblong plate; shell very small, planorbiform. Recent. Single genus: Homalogyra, whose true position is uncertain.
Fig. 273.—Solarium perspectivum Lam., Eastern Seas.