IIOO PSEUDODON 



with strong, irregular, concentric growth lines ; epidermis 

 (lark brown or blackish, subshining ; teeth single in each valve, 

 small but elevated, rounded, compressed ; muscle scars shal- 

 low ; nacre whitish ; pallial line sinused behind. 



Length 62, height 26, diam. 20 mm. 



Rivers of Nankin. 

 Monocondykca nankingensis Heude, Jl. de Conch., XXII, 1874, 



p. T16; Conch. Fluv. Nank., I, 1875, pi. iv, fig. 9. 

 Pscudodon nankingensis Simpson, Syn., 1900, p. 839. 

 Monocondykca nanquincnsis P.ETee, Conch. Sam., Ill, 1890, 



p. 174. 



A single, badly worn author's specimen of this species is in 

 the X'ational Museum collection, which is more pointed behind 

 than the figure. It is much inflated and the umbonal region is 

 scarcely elevated above the general outline. 



PsEUDODON SECUNDU.S Heude. 



Shell subsolid, elongated, subrhomboid, inflated, inequilat- 

 eral : umbonal region slightly elevated ; posterior ridge strong, 

 subangled, ending in a point near the base line ; anterior end 

 rounded ; dorsal' outline lightly curved ; base line nearly 

 straight ; posterior slope obliquely subtruncate ; epidermis 

 brownish, somewhat shining ; teeth single in each valve, sub- 

 compressed, triangular, elevated ; muscle scars well marked ; 

 nacre bluish-tinted, dirty flesh-color in the cavities ; pallial line 

 having a distinct sinus behind. 



Length 82, height 30, diam. 30 mm. 



Length 73, height 33, diam. 25 mm. 



River Hoae, China. 

 Fseudodon sccundus Heude, Conch. Fluv. Nank., Ill, 1877, 



pi. xviii, fig. 38. — Simpson, Syn., 1900, p. 840. 

 Unio sccundus P.^tei., Conch. Sam., Ill, 1890, p. 167. 



The first of the above measurements is that given by Heude 

 and I am inclined to think that the diameter is too large in 

 proportion to the rest of the shell. The second measurement 

 is from an author's shell in the National Museum. The spe- 

 cies is close to nankingensis, but is more solid, less elongated in 

 proportion, and has lighter colored, smoother epidermis. 



