SPECIAL llEPORT 



ON 



THE LIFE-HI8T0KY OF THE COMMON CLAM, 



MYA ARENARTA. 



BY PKOF. JAMES I,. KELLOGG. 



On several occasions in past summers I have noticed, in June 

 and July, on the eel-grass and Ulva in the vicinity of Woods Hole, 

 Massachusetts, some very small bivalves which were attached by 

 a byssus. The outline of the shell was such as to suggest a 

 similarity to the long necked, or soft clam, Jlya arenaria, and yet 

 the differences were considerable so far as form was concerned. 

 The whole outline was rounded, and the umbones prominent and 

 widely separated, while in the adult clam the shell is elongated 

 from before backward, the inconspicuous umbones approaching 

 each other closely near the median line. The character of the 

 hinge might have determined the matter, but it Avas so small and 

 fragile in the few specimens which I had picked up in the search 

 for other material, that examination was difficult and uncertain. 

 I had always had a suspicion, however, that a study of these forms 

 would show them to be the young of our common clam. 



Among the numerous notes and papers by the late Professor 

 John A. Eyder, of the University of Pennsylvania, I find a short 

 description of the young Mi/a attached by a byssus." A few in- 



*American Naturalist for Jaauary, 1889, embryological notes. 



