114 ORTMANN — AFFINITIES OF CAMBARUS. [April i 3j 



Virginia, Maryland, Pennsylvania and New Jersey ; and in the 

 south, where C. spinosus and erichsonianus cross over from the 

 Tennessee River drainage into that of the gulf and the Atlantic 

 Ocean in Alabama, Georgia, South and North Carolina. These 

 latter cases are continuous, the same species being found in both 

 drainages, while in the former case discontinuity is implied, C. 

 limosus being cut off and isolated from the rest of the range of the 

 subgenus. 



Generally speaking, this subgenus seems to belong to the 

 great rivers of the interior basin, its center lying about in the 

 region where the rivers Missouri, Mississippi, and Ohio come 

 together, that is to say, in the states of Mississippi, Kentucky, 

 southern Illinois, and southern Indiana. From this center it 

 spreads out in the directions of these rivers and tributaries, chiefly 

 toward the North and Northeast. However, the area remained not 

 restricted to the Mississippi drainage, but crossed the divides into 

 other systems in the following cases : From the Tennessee River 

 two species {spinosus, erichsonianus} have crossed over into the 

 Gulf and Atlantic drainages, and from the upper Ohio drainage 

 another species (limosus) has crossed over into the Chesapeake and 

 Delaware Bay drainage. Another species (mississippiensis) is found 

 in the Gulf drainage (outside of that of the Mississippi River) in 

 the state of Mississippi. In the North the area largely extends 

 into the drainages of the great lakes, and even into that of Hudson 

 Bay (through the Red River of the North and Winnipeg Lake). 



Studying the distribution of the single sections, the following is 

 to be remarked. The most primitive section (that of C. /imosus) 

 is marked by discontinuity : C. limosus being found on the Atlantic 

 coast plain, C. pellucidus, indianensis, sloanei in Kentucky and 

 southern Indiana, C. harrisoni in Missouri. This discontinuity, 

 chiefly the isolation of C. limosus, is accompanied by morpholog- 

 ical isolation, the latter species possessing in its spinosity a charac- 

 ter, that only recurs in the allied, but otherwise peculiar species, 

 C. pellucidus. This latter species, as well as C. sloanei, indi- 

 anensis and harrisoni, undoubtedly are the last remnants of 

 the primitive stock of the subgenus in its original home, i. c, 

 in the central basin formed by the three great rivers. Thus the 

 geographical distribution of the limosus-section confirms the char- 

 acter of antiquity : most of the species remain in the original 



