May, 1893.] MOLLUSKS OF THE DEATH VALLEY EXPEDITION. 283 



Helicina tropica Jan. 



Brownsville, Tex. (Mas. No. 123628), William Lloyd. 



A single example. 



Class PELECYPODA. 



Order TETRABRANCIIIATA. 



Suborder SUBMYTILACEA. 



Anodonta nuttalliana Lea. 



Keeler, Calif. (Mus. No. 123629), T. S. Palmer. 



One semifossil example. 



Unio anodontoides Lea. 



Brownsville, Tex. (Mus. No. 123630); Mier, Tamaulipas, Mexico, May 4, 1891 (Mus. 

 No. 123632), William Lloyd. 



The Brownsville examples are less elongated than usual in this species. 

 The Mexican specimens are full grown and of the usual proportions. 



These localities are believed to be much farther south than heretofore 

 reported. 



Unio berlandieri Lea. 



Mier, Tamaulipas, Mexico (Mus. No. 123631), William Lloyd, May 4, 1891. 



The examples of this species are nearly full grown adults and of the 

 characteristic aspect. 



Suborder CONCHACEA. 



Pisidium occidentale Newc. 



Oasis Valley, Nevada (Mus. No. 123633), Dr. C. Hart Merriam, June 2, 1891. 



Several examples. The above place is on the western edge of the 

 Ealstou Desert, in Nye County, Nevada. 



