216 TESTACEOUS MOLLUSCA, 



brown and obscurely rayed ; beaks undulated, nacre pearly-white 

 and irridescent. 2 J . . 3|-. — China. 



A. Benedictensis. Lea. — Symphonota B. Lea. in Am. 

 Ph. Tr. 1837. t. \6.f. 48. Trapezoidal, transverse, inequilateral, 

 rather compressed, very thin ; dorsal line nearly straight ; forming 

 an obtuse angle at each extremity, ventral edge scarcely arcuated ; 

 beaks somewhat prominent and granulated at the tip ; cuticle shin- 

 ing yellowish olive; nacre bluish white and irridescent, scars scarcely 

 perceptible, 2-J-..3J-. — Lake Champlain. 



A. Nuttaliana. Lea. on U. 2. p. 77 '. t. 20. f. 62. Winged, 

 elliptical, flattened on the side and enlarged on the umbonal slope, 

 ventral edge subincurved ; inequilateral, smooth, thin : beaks com- 

 pressed and undulated at the tip : umbonal slope furnished with 

 several impressed lines : cuticle smooth, polished, having a dark 

 broadband at the line of growth near the margin: nacre white. 



lJL 9 3 



Non-Symphonote. — A. Oval. 



A. Cygnea.* Lam. 1. — Mytilus C. Lin. 1158. — D. p. 

 315. — W. t. 12. f. 32. Oval, tumid, rounder and ventricose pos- 

 teriorly, compressed and more or less angular anteriorly, cuticle 

 olive green ; in the young the anterior slope is more dilated and 

 compressed. — Variety 1. Myt. Cellensis. Schrce. t. 2.f. 1. — 

 A. Sulcata. Lam. 3.— Turt. Man. t. \.f. 8. Large, ovate- 

 oblong, very ventricose, thin, brittle, rather produced anteriorly, 

 upper and lower edges nearly parallel and straight. — Variety 2. 

 Very like the last ; but shorter and the lower edge rather more 

 rounded. — Variety 3. Pen. 4. t. 67. f. 78. Very like the two 

 former, but shorter and the lower edge still more rounded. — Variety 



4. A. Piscinalis. Drap. t. \2.f. 2. Moderate, rather rhombic- 

 oval, ventricose, rather thick, often beautifully coloured, produced 

 anteriorly with the wing more compressed and elevated. — Variety 



5. Rossm. t. 20. f. 284. Moderate, oblong, rather rhombic, 

 rather compressed, brownish, much produced anteriorly, very short 

 and rounded posteriorly. — Variety 6. Intermedia. Lam. 10. 

 Ross. t. 3f 68. Moderate, obovate, obliquely truncated anteriorly, 

 compressed, striated, brownish green, and yellow zoned. — Variety 

 7 . A. Ponderosa. Rossm. 4. t. 20. f. 282. Moderate, ovate, 

 rather rhombic, ventricose thick, solid rough, internally white, 

 anterior slope subangular and rather truncated at the anterior ex- 

 tremity, covered with a calcareous deposit. — Variety 8. Small 

 elliptical ovate, brittle, rather produced anteriorly : short and 

 rounder posteriorly. 7. — Europe. 



A. Anatina. Lam. 22. — Mytilus A. Lin. 1158. — D. p. 

 317. — Ch. f. 763. Ovate-oblong, fragile, posteriorly rounded, 

 anteriorly subangulated, with unequal transverse grooves ; beaks 



