TRIBE NYMPHACEA. 87 



under an olive epidermis, internally violet ; dorsal margin slopino- 

 posteriorly, with a rounded off acuniination, anteriorly sub-truncated; 

 ventral edge posteriorly rounded ; anteriorly slightly flexuous : 

 umbones blackish. 1-J^,.3^\^. — Peru and C. America. 



C. Trunculus.— DoNAx. T. Lam. 24. — Philip, p. 36.— Ch. 

 f. 253, 4.— Born, t, 4. f. 3. 4.—Knorr. 1. t. 7. f. 7.-~E. t. 262. 

 /. I.— Poll. 1. t. 19./.' 12, 3. Oblong wedge-shaped, thick, only 

 marked with obsolete minute longitudinal striae, posterior side 

 nearly thrice as long as the obliquely truncated anterior ; posterior 

 dorsal edge sub-rectilinear : a linear excavated lunule ; yellow, 

 (rarely lilac) often with paler radiating lines, and one or two violet 

 bands; inside usually violet. f..l3^. — Mediterranean. 



CRASSINA. 



Sub-orbicular, transverse, equivalve, sub-inequilateral, close; hinge 

 with two strong, diverging, 'primary teeth -m the riglit valve, and 

 two unequal ones on the other ; ligament external, on the longer 

 side. 



C. Sulcata.* Turt. B. p. 132. t. II. f. 1, 2.— Venus. S. 

 Ifont. p. 131. — La7n. 27. — C. Danmoniknsis. La^n. 1. — 

 Venus. D. llont. svp. t. 29./. 4. — D.p. ]67.~Bl. t. 75./. 7. 

 — JV. t. 7 . f. 21. Roundish, triangular, and slightly compressed, 

 white under a dark brown cuticle, with smooth strong regular equi- 

 distant concentric ridges ; beaks nearly central and inclining ; lozenge 

 lanceolate lunule nearly heart-shaped : inner margin glossy and 

 crenulated. 1 .. 1^. — Enqland.^ 



C. FuscA. i>e.sA.— Tellina. F. Poli. 1. t. 15./. 32, 3. 

 Solid, triangular, somewhat heart-shaped, brown, sub-equilateral, 

 with twelve or thirteen very regular large transverse grooves : lunule 

 impressed deep and smooth : white within and the margins toothed. 

 Mediterranean. 



C. ScoTiCA.* Mont. sup. p. 44. — Venus S. Lam. 55. — D.p. 

 167.— Lin. Tr. 8. t. 2./. 2,.—Twrt. B. t. 11./ 3, 4.— W. t. 7.f. 

 20. Ovate, heart shaped, with strong regular flattened concentric 

 smooth ridges, white, with a brown cuticle, and the margin entire. 

 1. — Scotland, England. 



2 The shell which has been considered by Amei'ican authors as 

 identical with the European species is most assuredly distijict. We 

 propose for it the name of C. Latisulca. Cordiform, convex, 

 thick, heavy, with about eleven much elevated concentric ribs, 

 which are much narrower than the interstitial grooves ; cuticle 

 black ; umbones eroded ; lunule ovate oblong, and as well as the 

 lanceolate lozenge, excavated. 1 . . \\. — N. America. 



