no. 3602 CRAYFISHES — HOBBS, HOLT, AND WALTON 49 



7(4') Jaws grossly unequal in size C. heterognatha 



7' Jaws similar in size 8 



8(7') Prostate longer than slender spermiducal gland . . . . C. ingens 

 8' Prostate shorter and lesser in diameter than spermiducal gland. 



C. philadelphua 

 9(1') Anterior body segments terete, fifth through eleventh segments de- 

 pressed (tennis racquet shaped) Xironogiton instabilius 



9' Body uniformly depressed, spatulate 10 



10(9') Deferent ducts enter ental end of spermiducal gland. 



Xironodrilus formosus 

 10' Deferent ducts enter midlength of T-shaped spermiducal gland. 



Ankyrodrilus . . 11 



11(10') Dental formula 3/4 A. koronaeus 



11' Dental formula 5/4 or 5/5 A. legaeus 



Genus Ankyrodrilus Holt, 1965 



Diagnosis. — Holt (1965, p. 10) stated: 



Branchiobdellid worms with two pairs of testes; paired nephridiopores on the 

 dorsum of segment III; at least nine distinct segments visible in dorsal view; gut 

 straight, with sacculations in segments II, III, IV, those of segments III and IV 

 the larger; aggregations of gland cells present in lateral portions of segments VIII 

 and IX; caudal sucker ventral; body depressed and tapering gradually from 

 anterior end to its greatest width in segment VI, VII or VIII; spermiducal gland 

 large with blindly ending bifurcated proximal portion, vasa deferentia entering 

 the median portion of the organ; bursa constricted between atrial and penial 

 sheath portions, giving the organ as a whole a reduplicated aspect; ejaculatory 

 duct absent; spermatheca composed of ectal duct, bulb and ental process. 



Ankyrodrilus koronaeus Holt 



Figures \2a-d 

 Ankyrodrilus koronaeus Holt, 1965, p. 11. 



Diagnosis. — "Upper jaw with three large teeth, subequal in length; 

 lower jaw convex, rounded at tooth-bearing border, carrying four 

 small, subequal teeth" (Holt, 1965, p. 11). 



Range. — Tributaries of the Roanoke, James, and New Rivers in 

 Montgomery, Giles, Craig, and Botetourt Counties, Va. 



Specimens examined. — More than 160 specimens in 22 collections 

 from the following stations: 14, 18, 19, 29, 30, 52, 69, 71, 72, 77, 87-93, 

 98, 110-112, and 125. These are in all the major drainages of the area 

 at elevations ranging from 402 to 750 m. 



Host and associates. — A. koronaeus was associated with Cambarus 

 acuminatus at stations 29, 30, 87-93, 112; with C. 6. bartonii at all sta- 

 tions except 18, 30, 72, 88, 112; with C. I. longulus at 29, 30, 88-93, 

 112; and with C. seiotensis at 18, 19, and 72. 



Ostracod associates include An. ancyla at stations 88, 89, 92, 93; 

 Dn. ileata at 14, 18, 19, 29, 52, 69, 71, 72, 77, 98, 110, 125; Dn. truncata 



