90 THE NAUTILUS. 



members of the group into a continuous chain, one end of which is 

 U. cyUndricus Say, U. cylindricus Say var. strigillatus Nobis, U. 

 tuberculatus Barnes, U. conjugcms Nobis, U. b/andianus Lea, U. 

 asperrimus Lea, etc., and at the other extreme U. nodiferus Con. 



Anteriorily the shell reminds one of tuberculatus, except that it is 

 much more inflated in that region. Posteriorly it resembles blandi- 

 anus Lea = rumphianus Lea. It is wider and more inequilateral, 

 however, than that species. 



(7b be Continued.') 



PISIDIUM HANDWERKI, N. SP. 



BY DR. V. STERKI. 



Among a lot of Pisidia from the Lilycash Creek, Joliet, 111., col- 

 lected and sent for examination by Mr. J. H. Handwerk, in 1898, 

 there were a few specimens of evidently a new species. Yet it 

 needed confirmation by more materials. But all efforts of Mr. 

 Handwerk to secure more examples were in vain until a few weeks 

 ago, when he sent a lot of several thousand specimens from the same 

 creek, containing P. compression, fa/lax, cruciatum, punctatum, one 

 of the abditum group, and a few dozen of the Pisidium under consid- 

 eration, which is now confirmed as a n. sp. and named in honor of its 

 discoverer. 



Mussel small, rather rounded in outline, rather high, moderately 

 inflated ; beaks moderately large, somewhat papilliform ; superior 

 margin strongly, inferior moderately curved ; posterior rounded or 

 slightly truncated, anterior end rounded or with a slight indication 

 of an angle ; surface with dense, almost regular and sharp striae, 

 and with a silky gloss, tops of beaks smooth and shining, slightly 

 flattened ; color of epiconch pale to yellowish horn ; shell rather 

 strong, nacre colorless or whitish, hinge stout, strongly curved, plate 

 moderately broad, lateral teeth stout, rather high, short; cardinal 

 teeth small, line; the right one angular, with the posterior part 

 somewhat thicker, inserted in a longitudinal groove on the hinge 

 plate, formed by a sharp, tooth-like prominence along the lower edge 

 of the plate ; posterior cardinal tooth of the left valve rather long, 

 longitudinal, nearly straight, its ends sloping; anterior oblique, quite 

 small, or almost obsolete ; ligament rather small. 



