',V2 PROCEEDINGS OF THE NATIONAL Mi'si.i'M vol. laa 



0, h. bctrtonii was still present in the vicinity of the outlet, but occa- 

 sional individuals of 0. juvenilis were also there. Since L957, no 

 crayfish except 0. juvenilis has been observed by us in the entire lake. 

 We have not done any trapping, and it would be interesting to know 

 whether or not populations of C. 6. bartonii and ( \ acuminatus bave 

 found congenial niches at greater depths or whether, as we believe, 

 they have been totally replaced by 0. juvenilis. 



The presence of 0. juvenilis in New River is possibly due to very 

 recent migrations upstream from West Virginia. Had it been in 

 this portion of the river for some years, it is likely that with all of 

 the collecting thai has been done in the river in the Mountain Lake 

 area, it would have been encountered by one of as. While natural 

 migration might furnish an entirely plausible explanation for its 



occurrence here, the fact that the two specimens came from near a 

 fishing camp does not strengthen the possibility. 



Throughout the range o\' the species, firsl form males have been 

 collected in January and from A piil through November. Females 

 with eggs were found only in April. 



Although three ostracods and two hranchiohdellids are associated 

 with (). juvenilis at station 7, it seems unlikely that any of them 

 reached this area o\\ this crayfish. It seems more probable that the 

 infestations occurred after the introduction of the crayfish. 



The Ostracods 



It is necessary in most instances to rely on the structure of the 

 copulatory complex o( the male for the ^identification of entocytherids, 

 and (his cannot be satisfactorily done unless the specimen has been 

 cleared (temporary mounts in glycerine or permanent mounts in 

 balsam or some comparable medium). 8 The copulatory complex 

 consists of a pair of modified appendages that during amplexus are 

 so arranged that the clasping apparatus (tig. 7a) y^ each is directed 

 anteriorly but which at most other times are rotated 180° with the 

 clasping apparatus directed posteriorly. Orientation in descriptions 

 is that of the clasping position. Figure 7(/ represents a composite 

 copulatory complex that includes all of the 1 secondary sexual char- 

 acters utilized in the following key. 



Whereas in the crayfishes it is tin 1 male that is dimorphic, in the 

 entocytherids the female exists in two "forms": v i) the copulatory 

 or biunguis female, which, to our knowledge, is the form that is 

 always the partner in amplexing pairs (.and perhaps should be con- 

 sidered i lie last "larval instar") and may be recognized by the 4-seg- 



1 Vtosl o( our specimens have been prepared by dehydrating them with glacial 

 aoetio aoid transferring the Bpeoimen from formalin, water, or alcohol direotly 

 to the aoid olearing them in methyl salioylate and mounting them in balsam. 



