This genus of shells is very numerous in all seas, but chiefly in hot countries, where they are found of a larger size; they generally adhere by their base to rocks, stones, and marine substances, from which it is difficult to detach them. Shell oval or circular, sub-conic; summit right or more or less recurved anteriorly; the cavity simple, entire, more or less deep; the margin complete and entirely horizontal; a narrow muscular impression. Patella apicina. P. granatina. P. oculus. P. barbara. P. plicata. P. laciniosa. P. saccharina. P. angulosa. P. barbata. P. longicosta. P. spinifera. P. aspera. P. luteola. P. pyramidata. P. umbrella. P. plumbea. P. cærulea. P. radians. P. scutellaris. P. viridula. P. pectinata. P. Galathea. P. Safiana. P. testudinaria. P. cochlear. P. compressa. P. granularis. P. decaurata. P. Magellanica. P. stellifera. P. vulgata. P. mammillaris. P. lineata. P. leucopleura. P. notata. P. Tarentina. P. punctata. P. puncturata. P. Javanica. P. tuberculifera. P. miniata. P. pellucida. P. tricostata. P. Australis. P. cymbularia. _P. vulgata._ The common Patella. Pl. 2, fig. 1. Conic, summit obtuse and vertical; sometimes ribbed from the vertex to the margin with divergent striæ, sometimes striated without ribs; exterior dark brown or greenish, internal blue or purple radiations. _P. compressa._ The compressed or flat-sided Patella. Pl. 2, fig. 2. Oval, elongated, compressed on the sides, having the summit sub-anterior, well marked, and curved; exterior fawn colour, interior of a silvery hue. _P. deaurata._ The golden red Patella. Pl. 2, fig. 3. Sub-conic, summit more anterior, with a slight forward inclination; colour yellowish red. _P. cochlear._ The spoonlike Patella. Pl. 2, fig. 4.