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 ropert 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, strize 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.) 
450, B03. *\ 8.00.4 “ 
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, Ill., by Messrs. 
J. H. Ferriss and J. H. Handwerk.”’ (Sterki.) 
Remarks: ‘“Pis. vopert cannot be mistaken for any other 
