78 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 123 



group — in the San tee, there are 11 crayfishes, 6 ostracods, and 4 

 branchiobdellids ; in the Mountain Lake region there are 6, 13, and 12, 

 respectively (see table 3 for the numbers in the three river systems in 

 the area). Both species of crayfishes common to the two areas occur 

 in the Roanoke and James drainages, and C. b. bartonii is also present 

 in the New; both of the ostracods common to the two occur in the 

 James and one of them in the Roanoke drainage. Of the four species 

 of branchiobdellids present in the Santee, two of them, B. illuminatus 

 and C. philadelphica, occur in all three drainages of the Mountain 

 Lake area. 



Simonds has provided us with a summary chart of his findings and 

 the numbers of species present are recorded in table 3. Two crayfish 

 common to the two areas, C. carolinus and C. b. bartonii, are found in 

 the James and New drainages and the latter also in the Roanoke. Of 

 the two species of ostracods shared in common, Dt. jalcata and E. 

 internotalus, the former occurs in the Roanoke and the latter in the 

 James and New drainages. Of the five branchiobdellids found in the 

 two regions, B. illuminatus, C. jallax, and C. 'philadelphica occur in all 

 three drainages of the Mountain Lake area, C. heterognatha in the 

 James and New, and C. ingens in the New. 



Only three of the animals mentioned above occur in all five drainage 

 systems: one crayfish, C. b. bartonii, and two branchiobdellids, B. 

 illuminatus and C. philadelphica. 



The only comparative faunistic study of the drainage systems in the 

 Mountain Lake area is that of Burton and Odum (1945), in which 

 they compared the fish faunas of certain tributaries of the New and 

 James Rivers. Table 5 presents one of their comparisons and sum- 

 marizes our findings in the same streams. From the standpoint of the 

 fishes, Craig and Sinking Creeks and Craig and Spruce Runs share the 

 greatest number of species and Johns and Little Stony the least; in 

 contrast, using the totals of the three groups studied by us, Johns and 

 Little Stony have the most in common and Craig and Spruce Run the 

 least. Similarities and differences in our findings may be found in the 

 table. There is abundant evidence for multiple faunal interchanges 

 between the three river systems in the Mountain Lake area but these 

 data have never been brought together. Suffice it to say here that the 

 New River fauna is the principal component of the crayfish-entocy- 

 therid-branehiobdellid fauna of the region as here defined, and the 

 Tennessee basin has served as the chief pathway for the migrations of 

 stocks into the region. The Roanoke basin apparently has contributed 

 the least. Not only is the Roanoke the smallest and has the least 

 ecological diversity of the three river systems in the region, but also 

 there appear to have been fewer ancient ancestral stocks of crayfishes, 

 entocytherids, and branchiobdellids in it. 



