66 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 123 



metrical U around the Appalachian Mountains, extending from the 

 eastern Great Lakes area southward along the western slopes, eastward 

 around the southern portion of the Blue Ridge, and northward to 

 Maryland. The ancestors of this stock probably arose from a 

 southern Appalachian G. extraneus stock and spread northward on 

 both sides of the mountains. There is little doubt that C. acuminatus 

 arose in the foothills of the southern Blue Ridge and spread northward 

 along the Atlantic slopes to southern Maryland, an area in which it 

 is characteristic of the nonrifne portions of most of the lower mountain 

 and piedmont streams. In areas of the northern part of its range, 

 it even frequents streams in the lower coastal plain. In the Mountain 

 Lake area it occurs, like C. I. longulus, in the James and Roanoke 

 drainage systems. 



Cambarus carolinus is, in another way, equally as restricted in its 

 ecological requirements as is C. I. longulus, frequenting ground water 

 which it reaches through burrowing. Like the latter, it gained access 

 to the area along the western slopes of the Appalachian system, if 

 not from the south then from an original home to the west, probably 

 not far from this area. This crayfish habitually leaves its burrows 

 after dark following or during rains and often wanders some distance 

 from its tunnels. Not infrequently it has been seen crossing roads 

 and crawling about open areas where there are few or no obvious 

 burrows; consequently, an absence of standing surface water is not a 

 serious deterrent to the migration of this crayfish, and, therefore, it 

 is not surprising to find that it has crossed the divide into both the 

 New and James watersheds. 



Although Orconectes juvenilis is native to the Ohio drainage system, 

 its presence in the Mountain Lake area is almost certainly attributable 

 to introductions. It has demonstrated a remarkable vigor both in 

 Mountain Lake proper, where it has apparently brought about the 

 expulsion of other crayfishes, and in Potts Creek, where it seems to be 

 making notable progress in taking over most of the crayfish niches. 

 The sources of the introduced stocks have not been ascertained, but 

 it is highly probable that the animals were obtained from either 

 (or both) the New or Tennessee systems in West Virginia and Virginia, 

 respectively. To summarize briefly, the presence of the crayfishes 

 in the Mountain Lake region may be explained as follows : 



Cambarus acuminatus — by migrations along the Atlantic slope from the southeast. 

 Cambarus b. bartonii — originated in or near the area. 



Cambarus carolinus — originated in the area or by migrations from the southwest. 

 Cambarus I. longulus — by migrations from the southwest via the Tennessee and 



New Rivers to the Atlantic slope, probably along the James, and from it to 



the Roanoke. 



