122 ORTMANN — AFFINITIES OF CAMBARUS. 



[April 13, 



far to the northeast. This species has followed, in its dispersal, 

 chiefly the direction of the strike of this mountain chain, and 

 reaches now from Tennessee to Maine and New Brunswick. East- 

 ward, it hardly decends to the Atlantic plain, at any rate it does 

 not spread over it, and westward it goes as far as Indiana, always 

 preferring smaller streams in mountainous or hilly regions. 



C. bartoni possesses several marked varieties, chiefly at the south- 

 ern and southwestern extremity of its range, in Kentucky, Ten- 

 nessee and northern Georgia ; one variety (robustus) seems to 

 follow the northwestern edge of the range of the main species, 

 from Ohio through northwestern Pennsylvania to western New 

 York (and in Canada). This variety has also been reported from 

 Maryland and Virginia, but I doubt that this is actually the same 

 thing (see below, p. 135). 



Besides, there are three other species in this section, which are 

 closely allied to C. bartoni. One of them, C. acuniinatus, is found 

 in North and South Carolina, at the southeastern edge of the range 

 of C. bartoni ; the second, C. latimanus, fringes the southern and 

 southwestern extremity of the area of C. bartoni in South Carolina, 

 northern Georgia, northern Alabama, and central Tennessee ; and 

 the third, C. longulus, is apparently a form belonging to the high 

 mountains, being found in the middle of the southern part of the 

 main range of C. bartoni along the highest mountain chains of 

 North Carolina, Tennessee, Virginia, and West Virginia. Thus it 

 is beyond question, that we can regard these three species as local 

 forms of C. bartoni, the one belonging to the high mountains, 

 another being its southeastern, the third its southern and south- 

 western representative. 



While the first and second sections characterize the earlier stage 

 of the distribution of the subgenus, the third section expresses its 

 advance and dispersal over the eastern mountain system of the 

 United States. 



Finally, the fourth section (of C. diogenes) offers remarkable 

 conditions. Two of the species, belonging here ( C. carolinus and 

 monongalensis') are evidently a little more primitive than the rest. 

 C. carolinus seems to possess a wide range within the Appalachian 

 system. It is a true mountain form, and is found from northern 

 South Carolina to southern Pennsylvania, thus representing the 

 same direction of migration as C. bartoni. from southwest to north- 



