66 TESTACEOUS MOLLUSCA. 
edge curvilinear ; valves very but unequally convex, nearly smooth ; 
inside yellowish white, covered with radiating lines finely indenting 
the edge : ligament minute : hinge with two diverging cardinal teeth 
and an anterior lateral in one valve, a single cardinal in the other. 
T. Ints. Say. Jour. A. N. S. Phil. 2 p. 302. Oblong-sub- 
oval, very thin, pellucid, compressed, irridescent, white with gene- 
rally a rosy disc and one or two anterior rays, with numerous 
minute concentric wrinkles and minute oblique strong equidistant 
strie, which are abbreviated before and do not reach the narrowed 
and sub-acute anterior end: ventral edge straight opposite the 
beaks. -8,..43.—U. States. 
T. Atrernata. Say. Jour. A. N.S. Phil. 2. p. 275.—Say. 
Am, C. t. 65. f. 1. Oblong, compressed narrowed and angulated 
anteriorly ; white with numerous parallel equal equidistant trans- 
verse strize which are alternately obsolete on the anterior margin ; 
anterior dorsal edge sloping somewhat concavely to an obliquely 
truncated tip, inside tinged with yellow: anterior cardinal tooth 
emarginate, with lateral teeth, the posterior one approximate. 1}.. 
21.—U. States. 
T. Crystatyina. Chemnitz. f. 1948.—W. t. 3. f. 10. In- 
equivalve, one valve flat, the other convex; triangular-ovate, thin, 
white with raised distant concentric strize, the ventral edge rounded: 
anterior dorsal edge nearly straight and sloping, posteriorly rounded 
and rather the longer: a strongly marked fold in one valve, a cor- 
responding indentation in the other: slopes incurved: two lateral 
teeth in the flat valve. 2..1.—Allied to Belcheri. 
T. Sorpipa. Couthouy. Bost. J. of N. H. 2. tab. 3. f. 11.— 
Saneur. 8S. Gould. p.67.—Oval compressed, whitish under a 
horn-coloured epidermis, lines of growth numerous and distinct, 
posteriorly rounded, anteriorly shorter and slightly angular: 
within, semi-irridescent milk-white, hinge with a simple and bifid 
primary tooth in one valve, teeth usually obsolete in the other, a 
distant inconspicuous lateral tooth in each. 42%..149.— Boston. 
T. Serrata. Phil. p. 25.—Costa. p. xvii. no. 8.—T. Sur- 
cata. W.G.C.t. 47. f.1.—D.p. 89.—W.t. 4. f. 63. Ovate- 
triangular, equilateral, thick, dorsal edges nearly straight in their 
slopes ; anteriorly angulated, whitish but milk-white within, with 
raised transverse strize which become lamellar at the angle which 
bounds the hollow anterior slope which is smooth and narrow : two 
cardinal and two lateral teeth in one valve, two cardinal only in the 
other. 1}..14.—Mediterranean. 
T. Caucarga. Chem. f. 135.—D. t. 93.—W. t. 4. f. 43. 
Ovate, very brittle, white, glabrous, shorter slightly sub-angulated 
and inflected anteriorly, narrower and rounded posteriorly: a 
rounded cleft tooth in one valve shutting into a cavity in the other. 
3... 14.—Iceland. 
