no. 3602 CRAYFISHES — HOBBS, HOLT, AND WALTON 71 



juvenilis. Cambarincola branchiophila is apparently more common in 

 the New River system, 18 occurrences as compared to 4 in the James 

 and 9 in the Roanoke, but this may be a sampling artifact (table 1). 

 The species appears to belong to a primitive section of the genus, and 

 its closest relative is C. shoshone Hoffman (1963, p. 319) from the 

 Snake River drainage in Idaho. As a putatively relict species that 

 has survived in the area as a consequence of the adoption of the gill- 

 parasitic habit, the only clue as to its origin is the general importance 

 of the New River as the source of the branchiobdellid fauna of the 

 region from which the invasion of the upper reaches of the James and 

 Roanoke is easily understandable either through stream captures, 

 which have indubitably occurred, or the overland wandering of C. b. 

 bartonii. 



Ankyrodrilus koronaeus is likewise confined to the streams in the 

 area, occurring in all three of the drainages, but it has been found 

 outside the area in Botetourt County, Va., in the Roanoke drainage. 

 But A. legaeus, with only one record in the area from Wolf Creek of 

 the New River, is really a species of the Tennessee drainage, extending 

 from southwest Virginia to middle Tennessee, where it is found in the 

 Cumberland River drainage. At this time, the phylogenetic position 

 of Ankyrodrilus is obscure: one of us( Holt, 1965, p. 10) has pointed out 

 previously the similarities, mostly in body form, of the genus to 

 Xironodrilus and Xironogiton, yet a further consideration of the 

 male reproductive system leads to the tentative conclusion that 

 Ankyrodrilus may be most closely related to the eastern Asian Cir- 

 rodrilus. The genus would appear to be a survival in the southern 

 Appalachians of a formerly more widespread group and has reached 

 the Mountain Lake area from the Tennessee and Cumberland systems 

 by way of the Clinch or Holston Rivers. 



Pterodrilus alcicornus is a member of a genus, clearly an offshoot of 

 Cambarincola, that is centered in the southern Appalachian-Ozark 

 region with an outlier, P. distichus, which is found primarily in the 

 glaciated areas around the Great Lakes, and possibly another, P. 

 mexicanus, in southeastern Mexico. Pterodrilus alcicornus is a species of 

 the Tennessee system and has reached the New River from the southwest 

 and hence to the James. The species is not known from the Roanoke. 



Of the remaining species of the genus Cambarincola, C. holostoma is 

 known only from the James, Potomac, and New river basins. But it is 

 most common in the James system (Potts, Craig, and Johns Creeks), 

 with two records from Sinking Creek and one record (Hoffman, 1963, 

 p. 360) from the Potomac drainage. The conclusion that C. holostoma 

 is a specialized derivative of a C. philadelphica stock that arose in the 

 upper tributaries of the James River is inescapable. Cambarincola 

 ingens, common in the Tennessee drainage southward to northeastern 



