THE NAUTILUS. i: 
whose shell is—or appears to be—internal. But this one wore his 
shell upon his back for what purpose I do not know, for it was too 
small for protection, and the creature himself was so unpleasant to 
look at, no beauty of shell could redeem his ugliness. 
Red-brown in color, warty, even the inadequate shell was a dull 
greenish-grey ; not a single pretty feature! 
Only an enthusiast could have taken him up with a thrill of 
pleasure, instead of a qualm of disgust. 
Upon examination at home, it was determined to be Fissurellidea 
bimaculata ; yet the shell does not quite tally with the description in 
West Coast Shells. Internally it is white, outside gray-green with 
fine sculpturing; the rays running from the aperture to the edge 
are strong, the circular ribs faint, and the margin is not crenulated. 
F, bimaculata is said to be ¢ in. in length ; this one is more than double 
that size. And the dark spots on the sides are not visible. If the 
green stain could be removed perhaps they would appear; but as 
the size is too great for bimaculata, perhaps I have a Fissurella not 
credited to this coast. 
ON COLLECTING PISIDIA. 
BY DR. V. STERKI. 
Pisidia, and for a good part Sphaeria, are by far not sufficiently 
known, systematically as well as geographically. Requested to do 
so, and encouraged by prominent conchologists, the writer is going 
to work them up. Already some valuable materials are at hand ; 
thus the entire Pisidium-collection of Mr. E. W. Roper, numerous 
lots, most from Lake Michigan, sent by Mr. Bryant Walker, others 
from Mr. H. Prime and other conchologists, besides my own col- 
lection ; and some good results have so far been attained. Yet these 
materials are absolutely insufficient for a thorough study and knowl 
edge of these small mussels which, with all their minute size, are a 
very conspicuous and interesting part of our molluscan fauna. They 
should be studied in their different forms, considerably variable 
according to their habitats, and all kinds of waters should be searched 
for them all over the continent. 
Whoever has collected Corbiculidae assiduously will know that 
they are, as a rule, present in large numbers, wherever found. The 
