THE NAUTILUS. 95 



Bijidaria contractu Say. 

 Bifidaria procera Gld. 



LtjmncPAi obrussa Say. In a spring branch these and the two fol- 

 lowing were found. 

 Physa gyrina Say. 

 Pisidium sp. 



SFHJERIID2:, OLD AND NEW, II. 



BY V. STERKI. 



Pisidium peraltum St. The Nautilus, XIV, p. 5, 1900 



Specimens have been received from some other places : near Doug- 

 las Lake, Clieboygan Co., Mich., collected by Mr. H. B. Baker, and 

 Cedar Lake, Lake Co., 111., by Dr. F. C. Baker. But those from 

 Ky., 111. and la., formerly referred to peraltuin, are distinct and 

 range with the following : 



Pisidium fraudulentum, n. sp. — Mussel of medium size, barely 

 longer than high, somewhat oblique, rather well inflated ; superior 

 margin curved, passing with angles into the adjoining; supero- 

 anterior slope well marked, steeply oblique, straight or nearly so, an- 

 terior end a rounded angle situated near the ventral side, inferior 

 margin rounded, posterior truncate at right angles to the longitud- 

 inal axis ; beaks rather large, rounded or somewhat flattened on top, 

 moderately projecting over the upper margin ; surface dullish or with 

 a silky gloss, rather smooth, with fine, crowded, somewhat irregular 

 strijB ; color corneous to yellowish ; shell opaque or subtranslucent, 

 rather strong, hinge strongly angular, curved, very stout, its whole 

 surface rugulose ; right cardinal tooth angular, enclosing a deep ex- 

 cavation for the left anterior, often emarginate in the middle, its 

 anterior part thin, the posterior very thick and usually grooved ; left 

 anterior rather short and massive, strongly curved upward, with 

 apex pointed, the posterior short, steep oblique, slightly curved ; liga- 

 ment and resilium rather short, the latter strong. 



Long. 4.5, alt. 4.3, diam. 3 mm. (100 : 95 : 66). 



Habitat: Va., Ky., 111., la., Mo., Miss.; ditch on the Cameron Run, 

 west of Alexandria, Va., No. 602, types, and Roach's Run, Va., 



