"Second section, without a regular spire. The teeth in univalve shells, as the cowry, are ridges upon the aperture. ([Plate 1.]) In Voluta they are regular folds or plaits upon the columella.
"A fissure is a notch or slit, as in Patella fissura. ([Plate 3.])
"Some shells of this section are internally lipped, as Patella equestris; (Calyptræa of other authors, [Plate 3];) some are chambered, as the slipper-limpet; some are cap-shaped, having the apex much curved—these are the cap-limpets.
TERMS—
UNIVALVES.
"The vertex in Patella is as the superincumbent part of the shell.
"The epidermis is the outward skin that covers the surface of some shells.
"Fauces are narrow entrances, as at each end of the cowry.
"Tubercles are protuberances, or knobs, on the surfaces of shells.
"Striæ are raised or flat lines upon the surfaces of shells. When the surface is marked with lines longitudinally and transversely, it is decussated.