50 NEW UNIONID.E, MELANID.E, ETC., 



slightly sulcate before; umbonial slope raised and obtusely angular; posterior slope 

 rather broad, with two dark lines on each valve ; cardinal teeth small, erect, com- 

 pressed, crenulate and acuminate ; lateral teeth thin and somewhat curved ; anterior 

 cicatrices distinct, small and well impressed ; posterior cicatrices confluent and 

 slightly impressed ; dorsal cicatrices placed in the centre of the cavity of the beaks ; 

 cavity of the shell rather deep and wide ; cavity of the beaks shallow and obtusely 

 angular; nacre purplish and very iridescent. 



Soft Parts. — Branchial uterus not changed, but numerous very small ova were 

 found in the ovarium. Brancliice small and lightly curved below, inner ones rather 

 the larger, free nearly two-thirds the length of abdominal sack. Pal'pi large, ob- 

 lique, subtriangular, united half-way down the posterior edges. Mantle very thin 

 and without the caruncle which is so remarkable in loarvus and paulus, closely allied 

 species. Branchial opening rather large, with numerous small papillse on the inner 

 edges. Anal opening rather small, with numerous small papillae. Super-anal 

 opening large, colored on the edges and not united below in this specimen. Color of 

 the mass light salmon tint. 



Remarhs. — Only a single specimen was received from Dr. Showalter, but for- 

 tunately it was in alcohol, which gave the advantage of an anatomical examination ; 

 at once satisfying my doubts of its being distinct from parvus Bar. The epidermis is 

 of the same color, and the outline nearly the same, parvus not being quite so trans- 

 verse. The nacre is quite purple, a color I have never seen in parvus, which is 

 usually of a rich pearly white. Like parvus it has six or seven concentric undula- 

 tions on the tips, but these seem coarser in germanus. In the soft parts, although 

 this is a female, there is no sign of a caruncle below the branchial opening, so re- 

 markable in parvus. 



Unio rasus. PL 17, fig. 47. 



Testa liEvi, lata, inflata, valde insequilaterali ; valvulis crassis, antice crassioribus ; natibus prominentibus, 

 ad apices parum undulatis ; epidermide rasa, dilute straminea, eradiata ; dentibus cardinalibus com- 

 pressis, corrugatis, crenulatis, in utroque valvule duplicibus ; lateralibus praelongis, corrugatis sub- 

 reotisque ; margarita argeotea et parum iridescente. 



Shell smooth, wide, inflated, very inequilateral; valves thick, thicker before; 

 beaks prominent, somewhat undulate at the tips; epidermis smooth, pale, straw- 

 color, without rays; cardinal teeth compressed, corrugate, crenulate and double in 

 both valves ; lateral teeth very long, corrugate and nearly straight ; nacre silver 



white and somewhat iridescent. 



Proe. Acad. Nat. Sci., 1863, p. 189. 



Hab. — Assyria, C. M. Wheatley. 



Cabinet of Mr. Wiieatley. 

 Diam. -9, Length 1-2, Breadth 2-3 inches. 



