OSBORN. 



[Vol. XVIII. 



bottom were taken and the length of the shell in millimetres taken, 

 and the number of Cotylaspis counted. The results of this enu- 

 meration were as follows : 



These figures may be accepted as showing that, while the age 

 of the host has some influence in accounting for the number of 

 Cotylaspis present, it cannot be a determining factor, as is shown 

 clearly by the fact that we find fourteen parasites in a host 66 

 mm. long and only one in another 69 mm. long. 



There are some noteworthy differences between the facts of 

 distribution of Cotylaspis at Chautauqua Lake and in the locali- 

 ties that are noted by Kelley. He finds the parasite by no means 

 restricted to Anodonta, but while it is not as generally found 

 among the Unionidse as is Aspidogaster, still it is found in 24 of 

 the 44 different species of hosts that he examined, as against 37 

 hosts for Aspidogaster. He also finds that Cotylaspis is present 

 in six of the ten localities that he examined, Aspidogaster being 

 found in nine of them. In Lake Chautauqua, as noted, Coty- 

 laspis is not found outside of the genus Anodonta (the excep- 

 tions being too occasional to be counted). As some of the locali- 

 ties studied by Kelley are of the same river system as Lake 

 Chautauqua and are nearer the mouth of the river, and as the 



