SOME OBSERVATIONS ON THE HABITS OF 

 PECTEN DISLOCATUS. 



B. H. GRAVE. 



With the purpose of studying the habits of the scallop, Pcctcn 

 dislocatus, I collected many young specimens ranging from two 

 to ten millimeters in length and placed them in small glass aqua- 

 ria in the laboratory. 1 They were found in the harbor at Beau- 

 fort, N. C., well above the muddy bottom, clinging to eel grass. 

 They were usually attached by several strands of hyaline byssal 

 threads, which were exceedingly strong and elastic. 



Although the Pcctcn is so generally known as to make a 

 detailed description of its anatomy superfluous, yet a brief descrip- 

 tion of certain parts is deemed necessary. For a more detailed 

 study of the anatomy, reference can be made to a paper, by G. A. 

 Drew, on " The Habits and Anatomy of the Giant Scallop." 



By reference to Figs. I and 2, it may be seen that the shell is 

 rounded and eared. The ears make possible the long, straight 

 hinge line; which extends along their upper borders to their ex- 

 tremities. The right valve is slightly more convex than the left, 

 and near the anterior 2 ear, it has a deep notch. This one feature 

 mars the symmetry of the valves. Between the valves and just 

 beneath the hinge ligament, there is a pad of cartilage-like sub- 

 stance, which is compressed when the valves are closed. It 

 serves to open them quickly when the adductor relaxes (Fig. 3). 



The form of the shell and the structure and arrangement of the 

 soft parts within, adapt Pecten to the swimming habit. It swims 

 by opening and closing the valves in rapid succession. By vary- 

 ing the position of the mantle so as to control the direction of 



1 Through the courtesy of Hon. Geo. M. Bowers, U. S. Commissioner of Fish and 

 Fisheries, I had the privilege of occupying a table in the Fisheries Laboratory, at 

 Beaufort, N. C., for two months during the summer of 1908. For this privilege and 

 for many kindnesses shown me by the Director, Henry D. Aller, I am glad to express 

 appreciation. 



2 The hinge line is here considered dorsal for convenience in description, although 

 it does not represent the true dorsal of the animal. 



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