No angle at the umbones; anterior side at least as large as the posterior; rows of white, hollow, elevated ribs, situated at regular distances, proceeding from the umbones to the margin, with the spaces between them of a reddish brown colour. _C. unedo._ The Strawberry Heart. Species with ribs armed with small crescent-shaped scales. _C. tuberculatum._ The tuberculated Cardium. Species not gaping, with large ribs armed with nodules. 2. Cardita. Twenty-one species. Lamarck took this genus from the Chama on account of several peculiarities in the shell as well as in the animal. It is not affixed to other bodies by its lower valve, but, according to De Blainville, lies exposed on the rocks. There is some difficulty in distinguishing this genus from the Venericardia, without carefully examining the position of the two teeth. Shell regular, thick, solid, equivalve, more or less inequilateral; summit dorsal, always very recurved anteriorly; hinge similar, formed by two oblique teeth; one short cardinal placed beneath the umbo, the other oblique, arched, marginal, and prolonged; ligament elongated, sub-exterior, and inserted; two very distinct muscular impressions. Cardita sulcata. C. ajar. C. turgida. C. squamosa. C. phrenetica. C. crassicosta. C. rufescens. C. calyculata. C. subaspera. C. nodulosa. C. intermedia. C. trepezia. C. bicolor. C. depressa. C. concamerata. C. sinuata. C. aviculina. C. citrina. C. sublævigata. C. corbularis. C. lithophagella. _C. crassicosta._ The thick-ribbed Cardita. Species elongated, a little gaping at the inferior margin; ligament concealed. _C. sulcata._ The furrowed Cardita. Pl. 10, fig. 3. Sub-cordiform or oval, more transverse than longitudinal; colour white, tesselated with brown; posterior depression heart-shaped; longitudinal, convex, transversely-striated ribs. 3. Cypricardia. Four species. Distinguished from the Cardita by having three teeth beneath the apices, and a callous lengthened tooth or ridge. Shell obliquely elongated, equivalve, inequilateral; valves striated, but never ribbed; hinge with three teeth beneath the umbo, and one lateral elongated tooth. Cypricardia Guinaica. C. angulata. C. rostrata. C. coralliophaga. _C. Guinaica._ The Guinea Cypricardia. Pl. 10, fig. 6.