18 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 123 



Cambarus acuminatus Faxon 



Figure 1 

 Cambarus acuminatus Faxon, 18S4, p. 113. 



Diagnosis. — Margins of rostrum gently converging from base to 

 apex, not thickened, and without marginal spines; areola never more 

 than six, usually three or four, times longer than broad with many 

 shallow punctations; suborbital angle acute. Chela with subovate 

 fingers bearing distinct median longitudinal ridges on upper surfaces; 

 fingers not conspicuously gaping and never provided basally with 

 conspicuous tuf t of setae ; inner margin of palm with two well-defined 

 rows of prominent tubercles. 



Range. — Atlantic watershed from southern Maryland to South 

 Carolina in the lower mountains, piedmont, and upper coastal plain. 



Specimens examined. — Approximately 235 specimens in 25 col- 

 lections from tributaries of the James River and North Fork of the 

 Roanoke River in Craig and Montgomery Counties, respectively 

 (sta. 20, 27, 29-33, 35, 87-93, and 112) at altitudes from 402 to 535 m. 



Associates. — Cambarus acuminatus was collected with C. I. longulus 

 at all of the stations except 87 and with C. b. bartonii except at 20, 27, 

 30, 31, 33, 88, 112. 



In the James drainage, ostracod associates include Dn. ardis at 

 stations 20, 27, 30-33, 35; Dn. ileata at 20, 29, 31-33, 35; Dt. suteri 

 at 27, 30, 31, 33, 35; E. internotalis at 30, 31, 35; and in the Roanoke 

 drainage the latter at 88, 90; An. ancyla at 88, 89, 92, 93; Dn. truncata 

 at 87, 88, 90, 91, 93; and Dt. falcata at 87-93, 112. 



In the James drainage branehiobdellid associates include C. philadel- 

 phica at stations 20, 27, 29, 32, 33, 35; A. koronaeus at 29, 30; C. 

 branchiophila at 20, 29; B. illuminatus and C. holostoma at 20; and in 

 the Roanoke drainage A. koronaeus, C. branchiophila, and C. philadel- 

 phica at 87-93, 112; B. illuminatus at 87; C.jallax at 87-89, 91, 92; 

 and Xd. jormosus at 88-92, and 112. 



Remarks. — This species is more abundant in the larger streams in 

 the Roanoke and James drainages, where it occurs in pools, under 

 larger stones, in debris among the marginal vegetation, and in sub- 

 merged tangles of roots along the banks. It is also found in tunnels 

 along the shore, particularly in areas where there are steep clay banks 

 on the outer sides of bends in the stream. In the Mountain Lake 

 area it shares such habitats with C. b. bartonii. 



Like C. I. longulus, most of the population of C. acuminatus dis- 

 appears from the shallow water of streams in November and does not 

 reappear until spring. Most, if not all, of the individuals retreat 

 into burrows that presumably they construct with the onset of cold 

 weather. 



In Virginia, first form males have been found every month of the 



