THE NAUTILUS. 119 



inflated comparatively, and of cheracteristic shape ; surface with 

 very fine, more regular striation, and generally more even dullish ; 

 color grayish to brownish, whitish to straw-colored in the young but 

 soon changing. 



Various places in Michigan ; Grand river, Lamberton creek, a 

 small stream, etc. (Kent co., Dr. Kirkland) ; a very similar form 

 from a ditch on Cameron Run near Alexandria, Va. (Sterki). 



Var. elevatum, n. Smaller than the type, shorter, well inflated, 

 anterior part higher, anterior end more rounded ; superior margin, 

 slightly or scarcely curved with sharply projecting angles before and 

 behind, which are, however obsolete in some specimens; color straw 

 to yellowish- horn. This is quite a characteristic form but seems 

 connected with the type by intermediate specimens. 



Creek and pond at Castalia, Erie co., Ohio (Sterki), Joliet, 111. 

 (Ferris and Handwerk); similar forms from other places. 



Var. quaJrulum n. Smaller, slighter, of more quadrate outlines 

 but with no sharp projecting angles ; supero-anterior slope rather 

 steep ; beaks not much prominent ; surface with rather fine, some- 

 what irregular striae ; color pale to grayish-horn ; shell thin and 

 somewhat translucent, hinge rather slight. 



This Pisidium appeared to be distinct from noveboracense ; yet 

 intermediate forms may be found. It is a form of ditches and 

 marshes, and widely distributed, as it seems ; quite common, e. g., in 

 the vicinity of New Philadelphia, Ohio (Sterki). 



A larger form, stouter, higher, more inflated, with the shell 

 scarcely translucent, was called proclive ; it may prove to be a real 

 variety. Ditches, New Philadelphia, O., and similar forms from 

 other places. 



Var. lineatum n. Smaller, shorter, somewhat oblique, moderately 

 inflated, especially so towards the inferior margin, somewhat triang- 

 ular in outlines ; beaks narrow, little prominent ; surface with rather 

 fine, subregular stria?, and usually with a few fine lines, dark lines of 

 growth ; color straw to yellowish, horn to reddish ; shell and hinge 

 rather slight. 



Reed Lake, Michigan (Dr. Kirkland), and similar forms from 

 elsewhere. This is somewhat analogous to Pis. conipressum var. ros- 

 tratum, of the same lake and it may be noted that the same is in- 

 habited by nearly typical forms as well as several rather different 

 forms, or varieties of both species; at least one of each has not I 

 described here. 



