Nos. IAND2.] COTYLASPIS INSIGNIS. g 



time we know nothing of the fluke till it is found in the mantle 

 cavity of the Anodonta at which time it has assumed the charac- 

 teristics of the adult. It is a strange and interesting fact that 

 Poirier found Platyaspis in the intestine of a turtle, but as the 

 form he found is fully matured .we are debarred thereby from 

 regarding the turtle as an intermediate host. It is possible that 

 the fluke happened in the turtle accidentally, and more likely than 

 that the turtle should be the usual final host. 



As to the relation of the fluke to the Anodonta, Leidy pointed 

 out that it is ectoparasitic, and it appears that it is rather a mess- 

 mate than a parasite. We can see that its work in constantly 

 sweeping up material from the surface of the kidney would be 

 favorable rather than otherwise to the mussel. And this habit is 

 clearly correlated with the greater numbers found in water that 

 is more dirty. The operation yields food for the fluke, and hence 

 the dirtier the water the more numerous they are, as we have 

 seen. 



In all the mussels which I have examined I have made a care- 

 ful search in the cavity of the kidney and in the pericardial cham- 

 ber for the double purpose of deciding whether Cotylaspis is in 

 the habit of locating in either of these organs, and also of ascer- 

 taining if there is any other fluke that dwells in these parts. In 

 regard to both of these enquiries I found, as a result of a very 

 great many observations, that not only is- Cotylaspis never found 

 there, but also that no other fluke is. This result was the more 

 unexpected since the closely allied fluke Aspidogaster is very gen- 

 erally found in the pericardium and connected organs in the 

 Unionidse, being reported by Kelley as more frequent than Coty- 

 laspis. I am convinced that Aspidogaster does not exist in Chau- 

 tauqua Lake, or if present is extremely rare, since I have been 

 familiar with Unionidse there for five years and it has not ap- 

 peared in that time. 



d. External Anatomy. 



Cotylaspis (see Figs. 3, 4 and. 5), as already noted, presents 

 two somewhat distinct regions, the body and the ventral sucker. 

 The latter is very conspicuous and underlies and supports the 

 former. As in all the members of the family Aspidobothridae the 



