28 AMERICAN CORBICULAD^i:. 



Like all the species of this genus which live in estuaries, it is 

 nearly entirely deprived of epidermis, some few remnauts of it 

 only existing on the margins of the shell. The C. maritima is 

 very much larger than any of the so-called marine Cyrenx known 

 to us, and is not likely to ]>e confounded with any of them. 



2J). Cyreiia motallilis, Deshayes. — Shell transversely rounded, 

 snbijuadrilateral, somewhat depressed, inequilateral ; anterior side sliort, 

 ohturie ; posterior side broadly truncate ; superior and inferior margius 

 straight, parallel ; beaks oblique, not eroded, approximate at apex ; striae 

 light, irregular; epidermis greenish; valves solid, interior white with a 

 broad patch of dark violet on the upper portion of the posterior margin ; 

 ligament elongated, cylindrical ; cardinal teeth unequal, oblique, bifid ; 

 anterior lateral tooth small, conical, posterior tooth somewhat obsolete, 

 more distant from the cardinal teeth. 



Long. 2.31 : Lat. 1.87 ; Diam. 1.43 inches. 

 " 58; " 48; " 37 mill. 



Hah. South America, in Peru. (Cabinet of Cuming.) 

 Ci/rena notubilis, Desh. Proc. Zool. XXII, 1854, 21. 



Mr. Cuming possesses the only specimen I have seen of this 

 species, which is found at the mouths of rivers. Compared with 

 C. ohscura it is more quadrangular and less tumid ; it difi'ws very 

 materially from C. maritima and C. anvmola, and it is much 

 larger and heavier than any other of the estuarian species. 



30. Cyrena floridaiia, Conrad. — Shell trigonal, inequilateral, 

 cuneiform ; anterior side the shorter, somewhat pro- 

 Fig. 21. duced, rounded ; posterior side angular, subtruncate 

 at end, with an obtuse fold near the margin ; basal 

 margin curved, irregular ; beaks small, approxi- 

 mate at apex, curved inwardly, entire ; lunula 

 somewhat marked ; striae irregular, coarse espe- 

 cially towards the posterior margin where they 

 C.floridana. assume the shape of folds ; epidermis wanting ; 

 hinge-margin very much curved ; cardinal teeth 

 subequal, divergent ; anterior lateral tooth sharp f posterior lateral tooth 

 narrow, elongate ; valves solid, moderately inflated, exterior pale violet, 

 interior rough, whitish pink with dark violet bands on the margins ; sinus 

 not visible. 



Long. 1.12; Lat. 0.81 ; Diam. 0.4S inches. 



•i. 



28; " 20; " 12 mill. ^ 



