TRIBE NYMPHACEA. $5 
arcuated in the middle; inside stained with violet, the ventral 
margins dentated, the anterior crenulated: two cardinal and lateral 
teeth in each valve. #..14.—China.— When full grown less ine- 
guilateral than most of this genus. 
D. Srraminea. Schreter. 3. p.105.no. 12. t. 8. f. 4.—Gmel. 
3266.—D. p. 156.—W. ¢t. 6. f. 19. Obtusely wedge-shaped, con- 
vex, posterior dorsal edge much sloping, anteriorly very short, the 
edge convex and continuous to the ventral margin, the slope rounded ; 
yellow with two extremely short purple rays at the beaks, smooth 
except just at the anterior extremity, and bordering on the slope, 
where it is flexuously grooved and decussated by minute radiating 
striee, which latter are continued throughout the slope ; inside 
white, the slopes purple, the margin only crenulated anteriorly: a 
cardinal and two lateral teeth in one valve, two cardinal and a lateral 
in the other. 3..2. 
D. Semisutcata. Nobis in Z. P. 1843. Abbreviated cunei- 
form, uniform yellowish white, slightly tinged with red at the um- 
bones, posteriorly attenuated and smooth, the posterior dorsal edge 
much sloping: anteriorly ail but directly truncated, marked with 
transverse grooves, decussated by radiating striz, anterior edge 
nearly straight ; margins crenated: inside white, the disc pale 
pink, two lateral teeth in one valve, one in the other. 2.. 3. 
D. INcarnata. Chem. f. 259.—Gmel. 3265.—D. p. 153.— 
W. t. 6. f. 12. -E. t. 261. f. 6. Wedge-shaped, uniform pinkish 
flesh colour, truncated and marked with decussated wrinkled striz, 
posteriorly very finely striated longitudinally. 2..1.—Z'’ranquebar. 
D. Varrapitis. Say. Jour. A. N. S. Phil. 2. p. 305.—Say. 
Am. C.t. 61. f. 1. Triangular ; anteriorly obliquely truncated 
and cordate, the suture a little convex ; posterior dorsal edge nearly 
straight : the suture indented ; beaks a little prominent, sub-central: 
red, white, yellow or with linear reddish brown rays on a white or 
yellow ground, with most delicate longitudinal strize, which are ob- 
solete posteriorly. £..3—U. States. 
D. Fossor. Say. Jour. A. N.S. Phil. 2. p.306.—Say. Am. 
C.t. 61. f. 2. Sub-triangular, anteriorly short and rounded, pos- 
terior dorsal edge straight, beak little prominent, with all but invi- 
sible longitudinal strize, which are obsolete posteriorly, pale livid, 
with two whitish sub-anterior rays both within and without. 3.— 
New Jersey. Variety —Whitish.— Variety—Yellowish. 
D. Cauirornica. Conr. Jour. A. N. S. Phil. 7. p. 254. t. 
19. f. 21. Elongated, somewhat pointed at both ends, discs with 
very minute radiating lines, yellowish, obscurely rayed, a brown 
stripe on the posterior and anterior sub-margin: inside white and 
purplish brown, the margin crenulated. 2.—California. 
D. Scateettum. Gray. Ann. Phil. 25.—W. 8S. Donaa. 1. 
Elongated, flattened, thin, polished, yellowish, with purple rays, and 
