1254 DIPI.ODON 



Margaron fUnio) cffiilgcns Lea, Syn., 1870, p. 35. 



Diplodon eifulgens Simpson, Syn., 1900, p. 879. 



Unio eiirhyncJms Kuste:r, Conch. Cab. Unio, 1861, p. 237, pi. 



i.xxix, fig. 5. 



Apparently close to D. granosus, but more trapezoidal and 

 more solid. The peculiar pseudocardinals differ from those 

 of that species. Lea states in the Observations that this shell 

 is in the cabinet of Dr. Budd, but does not claim to have it in 

 his own. The type, from Dr. Budd, is now in his collection. 



Diplodon rufofuscus (Lea). 



Shell short rhomboid, convex, rather solid, inequilateral, 

 with low. scarcely inflated beaks ; post-dorsal part high, sub- 

 angulate where it meets the truncation of the posterior slope ; 

 posterior ridge full but widely rounded, ending in a rounded 

 point at the base line ; surface sculptured with concentric 

 ridges ; the umbonal region is marked with subnodulous, fine, 

 chevron-shaped bars, this pattern fading out on the body of 

 the shell, though over its whole surface there are traces of 

 nodules and radiating lines :' epidermis rich dark chestnut, 

 lighter in the umbonal region, subshining; left valve with two 

 low, subcompressed pseudocardinals and two curved laterals; 

 right valve with a high, subcompressed pseudocardinal, a 

 small one above it, and one lateral ; muscle scars small ; nacre 

 dirty bluish-white, thickened in front. 



South America. 

 Unio riifofuscus Lea, Pr. Ac. N. Sci. Phila., IX, 1865, p. y6; 



Jl. Ac. N. Sci. Phila., VL 1868, p. 282, pi. xxxix, fig. 96; 



Obs., XII, 1869, p. 42, pi. XXXIX, fig. 96. 

 Margaron (Undo) rufofiisciis Lea, Syn., 1870, p. 31. 

 Diplodon rufofnsciis Simpson, Syn., 1900, p. 880. 



This has much the appearance of a very short, solid D. gran- 

 osus, near which species it was placed in the Synopsis. The 

 type is in the Lea Collection, probably donated by Signor Paz. 

 after the twelfth volume of the Observations was published. 

 Perhaps a member of the lacfeolus group. There are a num- 

 ber of species, which possess characters of both groups and 

 might almost as well be placed in one as the other. 



