102 PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



This species is common about Key West on muddy bottoms. Numer- 

 ous specimens of various ages were obtained, the largest about C inches 

 in length. A single rather large specimen was secured in the market 

 at Havana. 



This species differs from C. nstus, and from the descriptions of C. den- 

 tiens, &c, in the entire absence of posterior canines in both young and 

 old examples. C. roseus, y^hich has no posterior canines, is very dif- 

 ferently colored. 



Indiana University, 



April 8, 1884. 



DESCRIPTION OF A NEW SPECIES OF SPH^RIUM. 

 By TE:inPlL.i: PRIME. 



Sphaerium costaricense Prime. 



Shell elongated, somewhat compressed, inequilateral; margins 

 rounded, sulcations regular, deep; epidermis dark brown; cardinal 

 teeth small ; lateral ones strong. 



Longitude, 12.0 ; latitude, 9.0 ; diameter, 6.0 millimeters. 



Habitat. — Central America in Yuriria Lake, West Costa Eica ; col- 

 lected by the late Prof. W. M. Gabb, and presented to the United States 

 Kational Museum by W. H. Dall. Number for the specimens on the 

 Museum register, 37251. 



This species is allied to 8. simile and S. striatinum. 



As far as I am aware this is the only instance known of the occur- 

 rence in Central America of the genus Sphcerium, properly so called. 

 As a rule this genus is replaced south of Mexico by the genus Lim- 

 osina, a section of the original genus S'phcerium. 



New localities for American Gorhiculidw. . 



S'phwrium striatinum Lam. San Joaquin River, California, near Stock- 

 ton, n. Hemphill. 



Pisidium virginicum Bourguignat. Yukon Eiver, Alaska, near the Rus- 

 sian mission. W. H. Dall. 



Pisidium abditum Haldemau. Pools on the north partof Unga Island, 

 Shumagin group, Alaska, between Popoff Strait and Coal Harbor. 

 W. H. Dall. 



Pisidium cequilaterale Prime. Bering Island, Commander group, Ber- 

 ing Sea, in a pond near the Ladyginsk village. Dr. Leonhard Stejne- 

 ger. Kotzebue Sound, in the clay covering the ice-clifts of Elephant 

 Point, Eschscholtz Bay ; fossilized. W. H. Dall. 

 Dr. Carl Agardh Westerlund, of Ronneby, Sweden, who is working 



up the land and fresh water shells of the Vega expedition, has described 



the following species of Pisidium in the Nachrichtsblatt der Deutschen 



