Williamson: Cravmsh ok Alli^chkw C<»fN'rv. 11 



the two transverse grooves meet along the middle line the areola is 

 oblitcnxti'J or linear. 



I. Cainhanis Inirtonii (y,^\^x\^:\\\'T,). Thisspecies is found in springs 

 and smaller brooks, and rarely in larger streams. It has been taken 

 in every ravine in Schenley Park and in a number of creeks through- 

 out the county. It is the most common species. Adult specimens 

 are uniform olive-brown in color, varying considerably as to shade. 

 V'ounger individuals are paler and have the abdomen regularly 

 mottled with brown. 



1. Cainbcinis hartonii, var. robiistiix Hagen. A few sjjecimens of 

 this variety have been taken from Stpiaw Run, which empties into the 

 Allegheny River about a mile and a half above Aspinwall. Observa- 

 tions indicate that this variety occurs in streams in which both /'«/- 

 toniidSiA propinquiis occur, the variety living in that part of the stream 

 where the two species are found. A collector starting at the head- 

 waters of Squaw Run would find hartonii : following the stream he 

 would soon notice robiistus among his captures ; then an occasional 

 prflpinquiis, till finally hartonii would become rare and disappear, then 

 rohustus would disappear, and near the mouth of the creek he would 

 find only the species propinqiius. If the collector chose to follow 

 on down the Allegheny River he would still notice o\\\y propimjuiis. 

 After reaching the Ohio, a few specimens from the ripples about 

 Neville Island would show him that- he had found another species, 

 r It stilus. 



3. Camhariis diogenes Girard. This species has been positively re- 

 corded from only one locality in the county. Fern Hollow, Pitts- 

 burgh. Two small specimens, probably this species, were taken from 

 burrows near Silver Lake, Pittsburgh. This is the commonest and 

 best known of the burrowing crayfishes. In life its color is olive, yel- 

 lowish, or greenish, and occasionally with the sides of the carapace 

 reddish. 



4. Camharits diihius Faxon. Specimens of this species collected in 

 Allegheny County have been sent to Dr. Walter Faxon for identifica- 

 tion. He considers them a local variety of this species, the Allegheny 

 County specimens having the rostrum much narrower than the types. 

 It has been taken in Schenley Park, in Fern Hollow, and from a spring 

 in Moon Township. Like diogenes this is a burrowing species. In 

 Fern Hollow during the autumn of 1898 the burrows were very numer- 

 ous. The chimneys about the opening of the burrows are on an aver- 



