78 THE NAUTILUS. 
Soft parts pink, especially so the foot and mantle edges; the liv- 
ing 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. 
Habitat: Maine, Rhode Island, Indiana, Illionis and Minnesota ; 
probably also Utah, California and Washington. 
Pis. roperi can not be mistaken for any other species except some 
forms of P. abditum Hald., but is at once distinguished from the 
latter species by its comparatively very broad beaks, the more elon- 
gated and more regular outline, the different appearance of its sur- 
face, usually the lighter color, the comparatively finer and shorter 
hinge, and, in the living animal, by the pink color of the soft parts, 
shining through the shell. It is the only speciesin which that color 
has been noticed so far, yet it remains to ascertain whether this be 
a constant character. But, however that may be, the species is 
valid. From several places specimens were obtained in company 
with P. abditum, and at once recognized as distinct. It was first 
noticed among Pisidia sent by Mr. E. W. Roper, in whose honor it 
isnamed. The largest and most beautiful specimens were collected 
in Higginbotham’s spring, near Joliet, Ill., by Messrs’ J. H. Ferris 
and G. H. Handwerk, who, from April, 1896, to this summer, re- 
peatedly forwarded me lots of living specimens together with P. 
abditum and another species. 
There are specimens from the Wasatch Mountains, Utah (sent by 
Mr. Bryant Walker), the Sierra Nevada (Mr. Roper), and Seattle, 
Wash. (Mr. P. B. Randolph), resembling the present species, 
although somewhat different from it as well as among themselves, 
and it is with some doubt that they were referred to P. roperv. 
Pis. fallax var. sepentrionale n. 
Differs from the type by the following characters: it is more 
rounded in outline, less inflated, the beaks are less prominent and 
without ridges; the striation is lesssharp; usuaily there are whitish 
dots and irregular blotches, evidently caused by disease. 
This seems to be a northern form. Pineand Mountain Rivers on 
the south shore of Lake Superior, collected by Mr. Bryant Walker ; 
Clear Water River, Minn., in company with rather typical and in- 
termediate specimens (Mr. H. E. Sargent), Little Madawaska River 
at New Sweden, and Aroostook River at Caribou, Me. (Mr. Olof O. 
Nylander), from the latter river in 1896 and ’98, and there are 
some specimens with distinct ridges on the beaks, or indications of 
such. 
