no. 3602 CRAYFISHES — HOBBS, HOLT, AND WALTON 29 



73, 75, 79-81, 116; E. kanawhaensis at 44, 126; and P. phyma at 3, 

 5, 44, and 64. 



Branchiobdellid associates include A. koronaeus at stations 18, 19, 

 72; A. legaeus at 81; B. illuminatus at 5, 19, 44, 59, 86, 97; C. branchio- 

 phila at 15, 18, 43, 55, 57, 58, 63, 65-67, 72, 73, 75, 79, 81, 86, 97, 104, 

 116, 126; C.fallax at 3, 5, 15, 18, 43, 54-58, 61, 63, 65-67, 70, 72, 75, 

 78, 79, 81, 86, 95-97, 126; C. heterognatha at 3, 5, 61, 63-67, 70, 72, 

 78-81, 86, 97, 105, 106, 116, 126; C. holostoma at 18, 19; C. ingens at 

 5, 15, 18, 54, 58, 61, 64, 67, 70, 72, 73, 75, 79-81, 86, 95, 97, 104, 116; 

 C. philadelphica at 3, 5, 19, 44, 50, 54-56, 59, 66, 106-109; P. alcicorwus 

 at 3, 5, 15, 18, 19, 43, 58, 61, 63-67, 70, 72, 73, 75, 79, 81, 86, 95, 97, 

 104, 105; and Xg. instabilius at 3, 5, 44, 54, 61, 64, 86, 95, and 97. 



Remarks. — In the New River system, this crayfish vicariates for 

 C. acuminatus of the Roanoke and James drainages, and with the 

 absence of the riffle-inhabiting C. I. longulus invades such habitats to 

 a greater extent than does C. acuminatus. In marked contrast to 

 C. I. longulus, C. sciotensis seems to be active throughout the year, 

 never burrowing except to excavate shallow depressions beneath rocks. 



First form males have been collected in March, April, and June to 

 October. Females with eggs were found in July and August, and 

 with young in August. 



Genus Orconectes Cope, 1872 



Diagnosis. — First pleopod of first form male terminating in two 

 parts, which may be straight or gently curved, short or long spines, 

 blades, or subspatulate projections. If terminals bent so much as at 

 right angle, bend never accomplished adjacent to shaft. Male with 

 hooks on ischiopodites of third pereiopods and occasionally on those 

 of fourth. Third maxillipeds not conspicuously elongate and ischiopo- 

 dite with row of teeth along mesial margin. 



Orconectes juvenilis (Hagen) 



Figure 6 

 Cambarus juvenilis Hagen, 1870, p. 66, figs. 29-33, 157. 

 Orconectes juvenilis Hobbs, 1942, p. 352 [by implication]. 



Diagnosis. — Margins of rostrum subparallel or slightly convergent, 

 not thickened, and with pair of marginal spines at base of acumen, 

 upper surface provided with distinct, median, longitudinal carina. 

 Lateral surfaces of carapace with pair of spines immediately caudal to 

 cervical groove; postorbital ridges terminating cephalically in spines; 

 suborbital angles lacking. Inner margin of palm of chela with two 

 closely appressed rows of tubercles with others above. First pleopod 

 of first form male extending cephalad to base of first pereiopod when 



