174 TESTACEOUS MOLLUSCA. 
Division A.—Unio PRopER. 
With a cardinal and lateral tooth. 
Section A.—SyMPHONOTE.! 
U. Inruatus. Lea.—Sympuonota I. Lea’s Unio. vol. 1. 
p. 109. ¢. 14. Triangular ovate, inequilateral, ventricose, very 
thin, elevated into a broad high wing posteriorly, a small one an- 
teriorly, both connate; cardinal tooth single in both valves, lateral 
teeth bladed towards their termination; beaks slightly prominent ; 
ligament concealed ; nacre purple, cuticle brown with obsolete rays. 
22..44.—h. Alabama. 
U. Avatus. Say.—Lam. 28.—Swain. Hx. C. t. 7.—Lea on 
U.1.p.62.—Mya A. W.S.f.3. Triangular ovate, transversely 
wrinkled, rather compressed, moderately thick, elevated into a high 
wing and connate over the ligament; beaks scarcely prominent, 
cardinal tooth double in both valves, lateral tooth double in the 
left valve only and slightly curved : ligament concealed, nacre 
purple. 4-5. .6,%.—N. America.® 
U. Lzyvissimus. Desh. in Lam. 6. p. 558.—SympuHonora L. 
Lea. on U. 1. p. 58. ¢. 13. f. 23. Subtriangular-ovate, inequi- 
lateral, subventricose, finely wrinkled transversely, shining, thin, 
with two not very high wings, the anterior the larger, both con- 
nate; beaks scarcely prominent; ligament concealed; cuticle 
purplish brown, nacre purple and irridescent: cardinal and lateral 
teeth forming a curved line. 22%. .43}.—Ohio. 
U. Graciuis. Barnes in Sil. Am. J. 6.—Sympn. G. Lea.— 
U. Puanus. Barnes.—U. Fraeius. Swain. Z. Il. vol. 3. Sub- 
triangular-ovate, inequilateral, transversely wrinkled, rather com- 
pressed, thin, anterior dorsal edge connate, wing but little elevated, 
beaks scarcely prominent ; ligament concealed ; nacre pearly, 
violet-purple, irridescent, cuticle yellowish green. 2! ..3515.— Ohio. 
U. Compressus. Lea.—Sym.C. Lea on U.1. p. 64. t. 12. 
jf. 22. ‘Transverse, much compressed, elliptical, inequilateral, 
thin, posteriorly rounded, beaks slightly elevated, not decorticated, 
crowned with small double concentric elevations, tips almost white ; 
anterior dorsal edge rather elevated and angulated at its extremity : 
cuticle olive green with broad rays all over the disc, nacre pale 
salmon becoming bluish near the margin ; cardinal tooth promi- 
nent, lateral small. 2/.. 1-1,.— Ohio. 

1 To this division belongs the genus Hyrra of Lamarck. 
2 Add likewise the Lymnapr1A GiGaAs of Swainson. 
