tion; rostrum short, with marginal spines (one on each side near tip) 

 obscure or absent 72. 



70. No ridge on rostrum; areola very narrow; claws very long and slender, 



about three times as long as the basal part of chela; Kansas and Ark. 

 Orconectes longidigitus (Faxon) 

 With central lengthwise ridge on the anterior part of the rostrum; areola 

 short and wide; claws broad; Alabama 71. 



71. No lateral spines on carapace; sides of carapace almost straight 



Orcoyiectes compressus (Faxon) 

 With a small spine on each side of the carapace; sides of carapace curved 

 Orcoyiectes alahamensis (Faxon) 



72. Sides of rostrum incurved, with lateral spines turned upwards; Arkansas 



Orconectes mee\i (Faxon) 

 Sides of rostrum straight; lateral spines of rostrum not turned upwards 



73. 



73. Tips of first pleopod of male only slightly curved 74. 

 Tips of first pleopod of male shorter and much curved 75. 



74. Areola narrow; rostrum hollowed out; Ala. 



Orconectes validus (Faxon) 

 Areola broader; rostrum almost flat; central states 

 Orconectes virihs (Hagen) 



75. Chela w'ith small hairs; Kansas 



Orconectes pilosiis (Hay) 

 Chela without hairs, except for tuft at base; Kansas 

 Orconectes nais (Faxon) 



76. First pleopod of male reaching to the base of the third leg 77. 

 First pleopod of male reaching to the first or second leg 82. 



77. Tips of first pleopod of male rather thick and slightly split, tapering to a 



point 78. 



Tips of first pleopod of male deeply split and more slender throughout 80. 



78. Tips of first pleopod of male pointing obliquely in opposite directions; 



Kentucky, Ind. 



Orconectes sloanii (Bundy) 

 Tips of first pleopod of male crossing each other 79. 



79. Sides of rostrum straight; sides of carapace before cervical groove spiny; 



widely distributed 



Orconectes limosus (Raf.) 

 (Camharus affinis (Say) ) 

 Sides of rostrum concave; sides of carapace granular; Ind. 

 Orconectes indianensis (Hay) 



80. Rostrum almost flat, without a ridge; with a shoulder on anterior margin 



of first pleopod of male; N. Y., Penna. 

 Orconectes ohscurus (Hagen) 

 Rostrum somev;hat hollowed out; no shoulder on anterior margin of first 

 pleopod of male 81. 



200 



