398 Annals of the Carnegie Museum. 



state lines to the south and west respectively. The exact location of 

 the northeastern boundary in Westmoreland county has not yet been 

 ascertained, possibly it is formed by the Loyalhanna or Conemaugh. 



Like C. caroUiiiis, this species is a burrowing species and a chimney 

 builder. The holes are made in a similar way as those of C. caroliuus 

 but generally are not quite as complex, although more so than those 

 of C. diogenes. Swampy pastures and fields on the hillsides, with a 

 permanent supply of spring water, are the favorite localities, and such 

 places are often entirely undermined by the burrows, and thickly 

 studded with chimneys of C. monongalcnsis. 



There is no doubt that this species has a close genetic connection 

 with C. caroliuus, but it is certainly specifically different. I never 

 met with a case in which I was in doubt about these two species, the 

 peculiar color distinguishing them at once, and moreover, their mu- 

 tual geographic separation supports their specific validity. They 

 never have been found associated at the same place, the northwestern 

 escarpment of the Chestnut Ridge forming a sharp boundary between 

 them. 



The specific name C. inonongalensis, has been suggested by the fact 

 that most of the range of this species belongs to the drainage sys- 

 tem of the Monongahela River. 



4. Cambarus DIOGENES Girard. The Mud Crawfish. 



From the allied species, C. carolimts and monongalcnsis, this one is 

 at once distinguished by the shape of the rostrum and the areola, aside 

 from the color. The rostrum is more elongate and narrower, often 

 being lanceolate without a trace of an angle or sinus at the base of 

 the acumen, the latter being not at all marked. In other cases, the 

 acumen is distinguishable. The areola is "obliterated," that is to 

 say, the two lines confining the branchial regions are in actual contact 

 in the middle of the carapace for a certain distance. Sometimes how- 

 ever the areola is not quite obliterated, there being a narrow space 

 left between the two lines : this is chiefly the case with specimens 

 from Fayette county. For the rest, this species is easily recognized by 

 the tubercles of the inner margin of the hand, which always form more 

 than one row, generally two, often with traces of additional rows, 

 while in C. carolinus and C. monongalcnsis there is always one row 

 only. 



The color of C. diogenes differs entirely from that of either of the 



