886 TESTACEOUS MOLLUSCA. 



arched and rising at either end ; dorsal edge subrectilinear, rising 

 gradually but decidedly from behind ; anterior side very broad, the 

 wing much elevated ; posterior side narrow : no conspicuous umbonal 

 ridge; umbones oblique, not much projecting; ligament narrow; 

 nacre silvery, with a pinkish tinge, especially in front ; teeth pro- 

 duced, laminar, lateral. If ...2. Bug Is, Celebes. The umbones are 

 a little eroded in the only example knoum to me. It is, probably, 

 identical with the U. snperbiis of Lea (Am. Ph. Tr. 9, pi. 42,/. 11), 

 yet his description does not exactly apply. 



Unio corbis (t. 23, f. 43), Benson, MS. Oval, inequilateral, rather 

 thin, subventricose, concentrically zoned with bluish green and ochra- 

 ceous-yellow, rather glossy, smooth, except at the umbones, which 

 are adorned with longitudinally divergent slender corrugations, the 

 hinder lines of which incline anteriorwards, the front ones posterior- 

 wards ; a few similar wrinkles radiate subtransversely thence to the 

 dorsal end of the concave anterior slope ; ventral edge convex ; front 

 dorsal edge straightish, a little elevated; extremities rounded, the 

 front one rather broad ; nacre silvery ; umbonal cavity ample ; teeth 

 laminar, compressed. f...l^. Assam. Described from a single 

 valve. 



Unto aivlenus (t. 24, f. 9), Lea, Trans. Am. Phil. Soc. 1. 10, f 12 ; 

 on U. 3, p. 38. Oblong or oblong-elliptical, very inequilateral, not 

 very thick, rather compressed, rounded at both ends, ochraceous- 

 yellow with numerous dark green rays, that are linear or obsolete 

 behind, and broader in front, nearly smooth ; ventral edge retuse in 

 the middle ; no umbonal ridge ; umbones oblique, eroded, not elevated 

 above the dorsal line ; inside white, iridescent ; cardinal teeth solid. 

 1...2*. Tennessee. 



B. (Margaritana = Alasmodonta). No lateral teeth (p. 210). 



Unto Curreyiantjs (t. 24, f. 10). — Margaritana C. Lea, Trans. 

 Am. Phil. Soc. 8, t. 18, /. 40 ; on U. 3, p. 61. Small, transversely 

 oblong subtrigonal, peaked or subrostrated in front, bluntly rounded 

 behind, subinequilateral, solid, somewhat compressed, with a yellowish 

 brown cuticle, not variegated, concentrically wrinkled, with 2 or 3 

 enormous tubercular undulations on the umbonal region, from which 

 radiate tw T o blunt umbonal ridges (the dorsal one projecting more 

 outwards), the area between which is retuse, and the margin behind 

 each of which is indented ; ligamental edge not much sloping ; liga- 

 ment short ; inside white, reddish salmon-coloured, or purplish 

 liver-coloured; cardinal teeth strong, no lateral ones. -} ... lj-. 

 Tennessee. 



