1895. | NEW YORK ACADEMY OF SCIENCES. 67 
and Brontops, Marsh, are founded respectively upon male and 
female individuals of the Titanotherium robustum. 
Dr. J. L. Worrman then reported on the “ Expedition of 1895 
of the American Museum of Natural History,” illustrating his 
paper by many lantern slides. The expedition passed into the 
Uinta Beds of northeastern Utah, then between the eastern 
escarpment of the Uinta range and the Green River, into the 
Washakie Beds of southwest Wyoming. The most important 
result geologically was the discovery that the Brown’s Park 
deposit is of a much later age than the Uinta. 
BASHFORD DEAN, 
Secretary of Section. 
ADAPTATION OF THE SHELL OF CREPIDULA FOR- 
NICATA TO THE SHELL OF PECTEN JACOBAUS. 
By ARNOLD GRAF, Pu. D. 
(Read before the Academy of Sciences of New York, Nov. 11, 1895.) 
During August, 1895, Mr. Frank Walmsley, preparator, showed 
me a shell which he had collected, and he was friendly enough 
to permit me to take a careful sketch of it, in order to write 
a paper about it. The shell was found at Wood’s Holl, Mass., 
where I happened to be at the time. I express my best thanks 
to Mr. F. Walmsley, for his kindness in granting me the 
privilege. 
The shell in question is a scallop-shell, on which a specimen of 
Crepidula fornicata is attached. Crepidula is often found 
clinging to Limulus, lobsters, scallops and many different shell- 
fish. As arule Crepidula presents an entirely smooth surface, 
on which only the concentric growth-lines are conspicuous. 
In the present case, however, the Crepidula shell shows 
marked grooves and ridges on its surface, which run in right 
angles to the growth-lines. This is clearly an adaptation to the 
well-known ridges in the surface of the scallop. 
The case must be a rare one, as in order to get such long 
ridges we must assume that the animal clung to the scallop 
when it was quite young, and did not move away during its 
whole life. 
The mechanical cause of the ridges in the shell is very appar- 
ent. The edge of the soft ‘‘mantel ” was pressed unto the surface 
