1252 nlPI.ODON 



Unio nilotlnis SowKRr.v. Conch. Icon., X\'T, 1868, pi. lxxiii, 



^g- 374- 



An exceedingly variable species and one which seems to 

 be quite abundant. Bruguiere's figure in the Encvclopedie 

 Methodique fairly well represents a phase of this protean 

 shell. I feel quite sure that Bunker's Unio pfeiffcri is merely 

 a form of this with rather strong, chevron-shaped sculpture, 

 and it is quite probable that '^raniiUfcnis and rufofusciis are 

 only varieties of it. Usually, though not always, the more 

 strongly sculptured specimens have a dull brownish epidermis, 

 while the smoother forms are more glossv and sometimes 

 green-tinted. I think there can be no doubt that Lea's iiiitlti- 

 striatus is the equivalent of graiiosiis, 1)ut T do not believe 

 that this equals Wagner's Unio ellipticus. The entire group, 

 of wdiich this is typical, is very puzzling. 



DiPLODON SEMIGRANOSUS n. S. 



Shell rather small, irregularl}- long elliptical or long ovate, 

 subcompressed or convex, inequilateral, with a low rounded 

 posterior ridge, above which is a wide, shallow, radial sulcus ; 

 beaks slightly elevated above the dorsal line, not swollen, sculp- 

 tured with 18 or 20 slightly curved, broken or subnodulous 

 ridges ; surface with feeble, concentric sculpture, which is 

 crossed by exceedingly faint, radial lirae and in addition is 

 often subgranulous ; epidermis olive or yellow-green, some- 

 times nearly black in old shells, dull or subshining ; left valve 

 with one small, subcompressed pseudocardinal, a vestige of a 

 second behind it, and two remote laterals, the upper small ; 

 right valve with two compressed pseudocardinals and one 

 lateral ; nacre dirty bluish-white, somewhat thickened in front, 



San Paulo "River ; Ponte Grande ; Os Perus, Brazil. 



A large number of specimens of a little Diplodon were sent 

 by Dr. von Ihering to the National Museum from several lo- 

 calities, which T at first referred to D. grauosns with much 

 doubt. It is solider and less high than that species ; it is more 

 elliptical or ovate, sometimes being drawn out somewhat be- 

 hind ; it is greener-colored and not so granose as that species 

 often is. 



