TRIBK NYMPHACEA. 85 



arcuated in the middle ; inside stained with violet, the ventral 

 margins dentated, the anterior crenulated : two cardinal and lateral 

 teeth in each valve, l^.-l;^. — China. — When full grown less ine- 

 gnilateral than most of this genus. 



D. Straminea. Schrceter. 3. p. \05.7io. 12. t. 8.f. 4. — Gmel. 

 3266. — D. p. 156. — W. t. 6. J". 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 

 strife, 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, g . • f . 



D. Semisulcata. Hobis in Z. P. 1843. Abbreviated cunei- 

 form, uniform yellowish white, slightly tinged with red at the ura- 

 bones, posteriorly attenuated and smooth, the posterior dorsal edge 

 much sloping : anteriorly ail but directly truncated, marked with 

 transverse grooves, decussated by radiating striae, anterior edge 

 nearly straight ; margins crenated : inside white, the disc pale 

 pink, two lateral teeth in one valve, one in the other, f . . f . 



D. Incarnata. Chem. f. 259.— Gmel. 3265.— Z>. p 153.— 

 W. t. 6.f. 12. -J?, t. 261./". 6. Wedge-shaped, uniform pinkish 

 flesh colour, truncated and marked with decussated wrinkled striae, 

 posteriorly very finely striated longitudinally, f . • 1 . — Tranquehar. 



D. Variabilis. 'Sny. Jour. A. N. S. Phil. 2. p. 305.— Sa9/. 

 Am. C t. 61. y. 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 striae, which are ob- 

 solete posteriorly. ^ . . ^ — U. States. 



D. FossoR. 'Say. Juur. 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 striae, which are obsolete posteriorly, pale livid, 

 with two whitish sub-anterior rays both within and M^thout. 4.. — 

 New Jersey. — Variety —Whitish. — Variety — Yellowish. 



D. Californica. Conr. Jour. A. N. S. Phil. 7. p. 254. t. 

 19.y. 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. f. — California. 



D. ScALPELLUM. Gray. Ann. Phil. 25. — TF. S. Donax. I. 

 Elongated, flattened, thin, polished, yellowish, with purple rays, and 



