i 9 o 5 .j ORTMANN — AFFINITIES OF CAMBARUS. 121 



GEOGRAPHICAL DISTRIBUTION OF THE SUBGENUS BARTONIUS. 



This subgenus is characteristic for the mountainous regions of 

 the east of the United States, that is to say, for the Appalachian 

 mountains, but the more highly developed, burrowing species have 

 in part descended from the mountains, and spread largely over the 

 central portions of this country. The greatest number of species 

 is found in the southern extremity of the Appalachian system, and 

 there is no question that we have to regard this as the center of 

 origin of the subgenus. 



The two cave forms of the first section are widely separated from 

 each other. This indicates, on the one hand, that they are not 

 very closely allied, and, on the other hand, the discontinuity thus 

 displayed again indicates antiquity. The one, C. hamulatus, is 

 found in a cave in eastern Tennessee, that is to say, right in the 

 center of origin of the subgenus, while the other one, C. setosus, 

 comes from a cave in Jasper Co., Missouri (in the Ozark region). 

 This is very remarkable, and very likely indicates, that the center 

 of origin of the subgenus possibly includes the Ozark Mountains, 

 west of the Mississippi : this is further suggested by the reported 

 presence of C. carolinus in the northeastern part of Indian Terri- 

 tory, not far from the locality of C. setosus (see below). Conse- 

 quently, we are to regard C. setosus as the last remnant of the 

 primitive forms of the subgenus surviving in the western extremity 

 of the original home. 



We have regarded, morphologically, the second section of the 

 subgenus as the most primitive group of it : this view is supported 

 by the geographical distribution. C. extraneus is known from 

 northern Alabama, northern Georgia, Tennessee, and Kentucky 

 (see below, p. 134) ; C. jordani is found in northern Georgia; 

 and C. cornutus in Kentucky (locally, only in Edmonson Co.). 

 Thus all the localities are in or near the old center of origin of the 

 subgenus. The presence of C. extraneus in the Cumberland and 

 Tennessee river drainages, as well as in the Alabama river drain- 

 age indicates an old drainage feature, namely the Appalachian 

 river (see above, p. 116). 



The third section presents very interesting conditions, such as we 

 have noticed in several groups of the subgenus Faxonius. Here 

 we have apparently one widely distributed, typical form, C. bartoni : 

 this is found all along the Appalachian mountains and extends very 



