102 



OKHAMANDAL MARINE ZOOLOGY ^.EPORT 



In the case of Pinnoteres ostreum, recorded from the East Coast of America, the 

 female only is commensal with Ostrea virginica, whilst the male is free-swimming. 



It is interesting to note from the preceding that only in the case of Pinnoteres 

 margaritifercB is the carapace referred to as being much flattened. 



Specimens of Pinnoteres placunce, n. sp., are particularly characterised by being 

 so compressed dorso-ventrally as to be quite flat. This, of course, is exactly what 

 one would expect to find in a species commensal with a bivalve in which the valves of 

 the shell are so closely approximated as in the case of Placuna placenta. In this 

 connection it is interesting to note that P. placuncB and P. glohosus form two extremes 

 in the form assumed by the body. As we have seen, P. placuncB is remarkably 

 flattened, whereas P. glohosus, as the specific name implies, is globular in appearance. 

 These facts serve to indicate the plasticity of the members of the genus and the 

 readiness with which they adapt themselves to their surroundings. 



It will be noticed that P. pisum is more or less cosmopolitan, having been 

 recorded from England and from New Zealand ; it would seem that other species of 

 Pinnoteres are local variations of P. pisum. The specific and restricted distribution 

 of certain of the species, such as P. margaritifercB and P. placuncB, appears to confirm 

 'this idea. 



The following is a list of the species of Pinnoteres recorded up to date, as far as we 

 have been able to ascertain, with their respective hosts and the localities where they 



occur :- 



