292 PROCEEDINGS OF THE ACADEMY OF [1897. 



pearanoe, but not a Calyculina. Clessin's figures 1 and 2 are poor 

 copies from the Voy. Amer. Merid., but the original figures are not 

 good. 



We have named this species in honor of Dr. V. Sterki, who has 

 undertaken the difficult task of working up the North American 

 Pisidia. 



Pisidium vile n. sp. PI. VI, figs. 17, 18, 19, 20. 



Shell rather inequilateral, quite globose, of a yellowish corneous 

 color. Surface glossy, very finely and evenly striated; anterior end 

 a little straightened or truncate ; posterior end narrower, produced 

 and rounded ; dorsal and basal margins about equally curved. 

 Beaks large and full, projecting well above the dorsal margin. In- 

 terior bluish-white. Teeth in right valve : a strong, large posterior 

 cardinal, emarginate at tip, and a low, narrow, inconspicuous upper 

 anterior cardinal ; laterals very strong and high. In the left valve 

 a low anterior and lower posterior cardinal, the pit between them 

 wide and deep ; laterals double, unusually heavy and strong. 

 Length 26, height 2 # 4, diam. 2 mm. 



From a small creek in the " Prado," Montevideo, Uruguay. 



This form differs from Cyclas pulchella Orb. (Pisidium Dorbignyi 

 Clessiu), described from Maldonado, in being smaller, shorter, with 

 much more projecting, fuller beaks. The very large size of the pos- 

 terior cardinal tooth in the right valve, and the greater reduction 

 of the anterior cardinal, are conspicuous features. A large series 

 was collected. 



It also seems to be unlike any other Pisidia of " Archiplata," 

 judging from the descriptions and figures of P. Chilense Orb., P. 

 Laurieochce and Forbesii Phil. 7 



Thracia Rushii n. sp. PI. VII, fig. 30. 



Shell thin, rather fragile, inequilateral, inequivalve, the right 

 valve swollen, left valve much less so, and with lower beak than 

 the other. White, with a thin isabella tinted cuticle toward the 

 margins. Anterior end long, broadly rounded, dorsal and ventral 

 margins subparallel ; dorsal margin behind the beaks straightly 

 sloping, short, posterior end abruptly truncated. Pallial sinus 

 moderate. Hinge very slender and delicate; ossicle lunate, with 

 the ends blunt. 



Length 29, height 20, diam. 9"5 mm. 



7 Novitates Conchologica 5 , III, p. 489, pi. 105. 



