tae | 
64 THE CHICAGO ACADEMY OF SCIENCES. 
growth, which are raised into ridges on the ventral portion of 
the shell; umbones a little elevated, prominent, brownish in 
color and marked by four coarse, elevated ridges, the apex 
directed anteriorly; ligament short, narrow, very dark brown or 
chestnut in color; epidermis brownish, with numerous dark 
green rays of variable width extending from the beaks to the 
ventral border; cardinal teeth small, elevated, thick, striated, 
that in the right valve large, thick, longer than wide, that in the 
left valve smaller, narrow, saddle shaped; lateral teeth repre- 
sented by a thickening of the hinge line; anterior adductor 
muscle scar long and narrow, deeply impressed, striated; poste- 
rior adductor muscle scar almost as wide as long, scarcely im- 
pressed, confluent; protractor pedis muscle scar small, long and 
narrow, impressed; dorsal muscle scars situated on the poste- 
rior face of the cardinal teeth, large, deeply impressed; pallial 
line distinct; cavity of the beaks shallow; nacre bluish, tinged 
with salmon or pinkish on the anterior portion, iridescent. 
Length, 41.00; height, 23.50; breadth, 15.50 mill. (10085). 
a Stop l]U | St PE UU Be aaa 15.00 ‘* (10085). 
a 20,00; * 4 tS 00; s* 12.50 ‘* (10092) 
se 7 | aia 16.50. a 11:50 2a (8384); 
Animal; Yellowish white on foot, flesh colored on abdomen; 
mantle yellowish white edged with black; liver dark brown; 
ctenidia of medium size, rounded and united above for their 
entire length; labial palpi rather long, rounded, tongue shaped, 
narrow, flesh colored; siphons rather large, edged with black. 
Distribution: Great Lakes and Mississippi Valley. 
Geological distribution: Pleistocene. 
Habitat: Found associated with U. marginata. 
Remarks: After an examination of numerous specimens I 
am led to place ca/ceola in the synonymy of de/toidea. They 
occupy the same localities and have the same general shape, 
and the description of one will answer as well for the other. In 
the female the shell is more produced posteriorly and also 
a little wider; there is a decided ridge where the umbonal slope 
meets the sides of the shell. This is a common little mollusk 
and one which is easily distinguished by its small size, solid 
shells and bright green rays. The umbonal markings are large 
and well developed. Old specimens become very solid, and the 
epidermis changes to almost black. 
