Cardium indicum. C. Asiaticum. C. fimbriatum. C. aculeatum. C. tuberculatum. C. apertum. C. bullatum. C. echinatum. C. biradiatum. C. pectinatum. C. isocardium. C. angulatum. C. serratum. C. costatum. C. ringens. C. tennicostatum. C. psudolima. C. crinaceum. C. Basilianum. C. papyraceum. C. ciliare. C. levigatum. C. eolicum. C. elongatum. C. rugosum. C. unedo. C. medinum. C. tumotiferum. C. retusum. C. rusticum. C. Greendlandicum. C. crenulatum. C. minotum. C. scobinatum. C. cardissum. C. inversum. C. ventricosum. C. obtusum. C. fragum. C. lineatum. C. edule. C. latum. C. exigunum. C. rosenum. C. hemicardium. C. Junoniæ. C. muricatum. C. marmoreum. C. sulcatum. C. cifidium. · · · · · C. Mortonii.* C. substriatum.* C. Nuttallii.* C. Californianum.* C. quadragenarium.* C. Pennulatum.* C. pubescens.* 2. Genus _Cardita_. Pl. VII. _Animal._ Body suborbicular, terminated superiorly by a sort of hook; mantle but little open; foot terminated at its extremity by a part much narrower than the base; superior lobes of the branchiæ very short. _Shell._ Thick, solid, equivalve, more or less inequilateral; summit dorsal always much flexed anteriorly; hinge similar, formed by two oblique teeth, one short, cardinal or apicial, the other postapicial, long, lamellous and arcuated; ligament elongated, subexterior and inserted; two very distinct muscular impressions, united by a palleal band, narrow and semicircular. Inhabits the Mediterranean and American seas. Twenty-three living species. Four fossil. Cardita Ajar. C. squamosa. C. crassicosta. C. calyculata. C. nodulosa. C. trapezia. C. sulcata. C. turgida. C. phrenetica. C. rufescens. C. subaspera. C. intermedia. C. depressa. C. sinuata. C. citrina. C. orbularis. C. bicolor. C. concamerata. C. aviculina. C. sublevigata. C. lithophagella. · · · · · C. borealis.* C. incrassata.* 3. Genus _Cypricardia_. Pl. VII. _Animal._ As above. _Shell._ Obliquely elongated, equivalve, inequilateral; valves striated, not ribbed; distinguished from the Cardita by having three teeth beneath the apices, and a callous lengthened tooth or ridge. Inhabits the coast of Guinea and California. Five living species. Three fossil. Cypricardia angulata. C. Guinaica. C. coralliophaga. C. rostrata. · · · · · C. Californica.* 4. Genus _Hiatella_. Pl. VII. _Animal._ Unknown. _Shell._ Thin, elongated, subrhomboidal, equivalve, very inequilateral, gaping at its inferior edge, and at its posterior extremity; summit very anterior, and much flexed to the front; hinge formed of a single tooth upon one valve corresponding to an emargination in the opposite valve, or of a small tooth with a cardinal pit upon each valve; ligament exterior and dorsal. Inhabits the British seas. Two species.