THE NATURAL HISTORY SURVEY. 405 



appendages on the beaks, yet they are evidently identical." 

 (Sterki.) 



This Pisidium is not common in this area, and only a few 

 specimens have been found in Lilycash Creek, near Joliet, 

 (western region) by Mr. Handwerk. Further search will proba- 

 bly bring more to light, not only in that locality, but in others. 

 Heretofore it has been found only in the Ohio and St. Lawrence 

 drainages, but we must now add the drainage of the Mississippi. 



159. Pisidium roperi Sterki. Unfigured. 



Pisidium roperi STERKI, The Nautilus, Vol. XII, No. 7, p. 77, Nov., 

 1898. 



Shell: "Mussel rather large, strongly inflated when ma- 

 ture, very little so when young; oblong to ovoid in outline, 

 margins regularly curved with no projecting angles (in the 

 adult); scutum and scutellum scarcely marked; beaks moder- 

 ately posterior, very broad, surface somewhat glossy, with ir- 

 regular, not sharp, striae and some strongly marked lines of 

 growth; color of the dry shell straw to yellowish-horn, often 

 with one to seven fine, concentric lines of purple; shell rather 

 thin, nacre whitish, muscle insertions scarcely marked, hinge 

 comparatively fine and short; cardinal teeth quite small, the 

 right one moderately curved, slightly thickened at the poste- 

 rior end; the left ones very short; the inferior slightly angular, 

 truncated or pointed on top, the superior sometimes almost 

 obsolete; lateral teeth short, small, scarcely projecting into 

 the interior; ligament rather fine." (Sterki.) 



Length, 5.50 ; height, 4.40; breadth, 3.80 mill. (Sterki.) 

 4.50; " 3.70; " 3.00 " 



Animal: "Soft parts pink, especially so the foot and man- 

 tle edges; the living mussel appears pale red, but the color 

 soon fades away after the death of the animal; it is also very 

 pale, scarcely noticeable in the young, becoming more intense 

 with the age of the animal." (Sterki.) 



Distribution: "Maine, Rhode Island, Indiana, Illinois and 

 Minnesota; probably also Utah, California and Washington." 

 (Sterki.) 



Geological distribution: Pleistocene; Loess? 



Habitat: "The largest and most beautiful specimens were 

 collected in Higginbotham's Spring, near Joliet, 111., by Messrs. 

 J. H. Ferriss and J. H. Handwerk." (Sterki.) 



Remarks: "Pis. roperi cannot be mistaken for any other 



