SPECIES.
1. C. Shell suborbicular vex, base a little flattened; with nearly equidistant, raised, concentric lines, giv ing a slightly sulcated appearance to the surface, and generally a more conspicu ous elevated darker wave, marking the former year's growth of the shell. Epi dermis brown or ferruginous ; beak near er central and obtuse ; hinge with minute very oblique teeth, lateral ones very dis tinct, elongated, and considerably resem bling those of the next species.
Length seven-twentieths of an inch : breadth two-fifths : a specimen measured in length nearly three-fifths of an inch.
Plate 1. fig. 9.
Very much resembles Teilina Cornea of authors; is found in plenty in the river Delaware ; animal viviparous ; from one specimen three pale yellow active young ones were taken, the largest of which measured in breadth three twen tieths of an inch in the month of May.
2. C. Dubia. Shell oblique, subovate convex, concentrically wrinkled, very pale horn colour or whitish, with some times a darker, but not raised band, marking the preceding year's growth of the shell ; beaks placed much nearer one within whitish, primary teeth very distinct, in one valve two divarieating ones, in the other but one, exterior late ral laminal tooth very small.
Length, five-twentieths of an inch ; breadth, three-tenths.
Plate 1. fig. 10.
Inhabits the river Delaware in compa ny with C. ,Sintilis, and very much resem bles Tellina Amnica of Authors.
ewes CYRENA, Lam.
Shell triagonally rounded, turgid, in equilateral, equivalve, robust ; limbo eroded or decorticated; hinge three toothed in each valve ; lateral teeth two, of which one is placed nearer to the primary ones; ligament exterior placed on the longest side.
Oba.. This genus has been but lately constructed by Lamarck, to receive such shells of the former genus Cyclas as have three primary teeth on each valve.