_Animal._ Body creeping, ovate oblong, convex, round at both extremities; marginated with a coriaceous skin: the back covered by a longitudinal series of testaceous, transverse, imbricated, and moveable plates; head before, sessile, with the mouth placed below, destitute of tentacula or eyes; branchiæ placed round the body, under the margin of the skin; and orifice at the posterior extremity. _Shell._ Eight imbricated valves, nearly smooth, slightly carinated, and rounded at the margins: summit more or less marked and curved by longitudinal elongations. Inhabits the British and American coasts. Sixty-three species. Chiton fulvus. C. pisceus. C. ruber. C. lævis. C. spinosus. C. fascicularis. C. marginatus. C. crinitus. C. siculus. C. niger. C. spiniferous. C. coquimbensis. C. lumingii. C. granosus. C. glauco-sinctus. C. disjunctus. C. elegans. C. lineatus. C. sulcatus. C. bicolor. C. cerasimus. C. Magellanicus. C. marmoratus. C. nebulosus. C. olivaceous. C. latus. C. punctatus. C. viridus. C. cinerus. C. tunicatus. C. gigas. C. squamosus. C. Peruvianus. C. tesselatus. C. capensis. C. Carmichaelis. C. echinatus. C. striatus. C. lineolatus. C. chilensis. C. tuberculatus. C. hispidus. C. thalassimus. C. porosus. C. larvaformis. C. undulatus. C. luteolus. C. fuscus. C. minimus. C. cimex. C. ascellus. C. Icelandicus. C. fasciatus. C. setosus. C. variegatus. C. asselloides. C. indus. C. albas. C. castaneus. · · · · · C. Emersonii.* C. fulminatus.* C. amœna.* C. alternata.* C. sagrinatus.* 4. Genus _Patella_. Pl. IX. _Animal._ Body completely covered by the shell; head with two acute tentaculæ, and the eyes situated at their exterior base; branchiæ placed under the mantle and around the body. _Shell._ This numerous and beautiful genus of Linnæus has been subdivided into the several distinct genera of Fissurella, Emarginula, Navicella, Umbrella, Pileopsis, Calyptrea, Crepidula, Parmophora, and Ancylus; each of which possesses sufficiently well-defined characters to authorize a separation, by which they may be more easily distinguished from the still widely extended family of Patella. Oval, conic, or a little depressed, outside green or brown, sometimes radiated with various colours; having divergent striæ and concentric wrinkles, inside glossy, iridescent, with yellow or fawn-coloured, purple, blue, or brown radiations. Inhabits almost every coast. Forty-nine species.