528 On new Mollusca from Peru and Argentina. 



cliocolate bands of irreorular width ; whorls 4|^, ahnost planu- 

 late above, then shouldered and rounded below, the last 

 descending considerably in front and rather elongated towards 

 the base, smooth; suture impressed^ painted below with a 

 very broad, whitish-grey, spiral band ; umbilicus funnel- 

 shaped, deep; columella margin acute, almost erect, descending 

 in a curve ; labrum acute, slightly dilated below ; aperture 

 elongately ovate; interior of shell livid greyish brown, shading 

 to chocolate. 



Alt. 52, diam. maj. 42"5, diam. min. 36 mm. 



Aperture : alt. 39, diam. 22 mm. 



Hab. Contamano, Rio Ucayali, Eastern Peru. 



CorhiGula bermejoensis, sp. n. 



Shell subtrigonal, whitish cream-colour, almost smooth, 

 marked only with very fine concentric striae; dorsal margin 

 arched ; ventral margin gently curved ; anterior side rounded ; 

 posterior side rather abru))tly descending, angled below ; 

 right valve bearing a very oblique, marginal anterior and 

 two short, solid, posterior cardinal teeth and two curved 

 serrated laterals on either side ; left valve bearing two solid 

 and divergent anterior and a very oblique, slightly curved 

 and elongated, well-developed posterior cardinal tooth, and a 

 coarsely serrated curved lateral on either side. 



Long. 9, lat. 9'25 mm. 



IJab. Rio Bermejo, a tributary of the Rio Cliaco, N. Argen- 

 tina {Clark). 



Corhicula oppro.vimans, sp. n. 



Shell differing from C. hernujoensis, Preston, in its mucli 

 more ovate form, it being much more laterally produced on 

 either side, but es|)ecially anterior!}', than in that species; 

 it is also much more coarsely concentrically striate, and the 

 cardinal teeth are weaker, chiefly in the right valve. 



Long. 10 (nearly), lat. 11 (nearly) mm. 



IJah. Rio Bermejo, a tributary of the Chaco, N. Argentina 

 {Clark). 



