no. 3602 CRAYFISHES — HOBBS, HOLT, AND WALTON 63 



Range. — Michigan, Indiana, Kentucky, Virginia. The range of 

 Xd. formosus appears to be discontinuous; it is present in the James 

 and Roanoke Rivers but apparently absent in the New River. 



Specimens examined. — Approximately 30 specimens in 8 collec- 

 tions from the following stations: 10, 21, 88-92, and 112. Of these 

 stations 10 and 21 are on Johns Creek at elevations of 549 and 561 m, 

 and the remainder are on the Roanoke River and the lower reaches 

 of its tributaries at elevations from 439 to 543 m. 



Hosts and associates. — Xironodrilus formosus was associated 

 with Cambarus acuminatus at stations 88-92, 112; with C. b. bartonii 

 at 10, 21, 89-92; and with C. I. longulus at all stations. 



Figure 21. — Xironodrilus formosus: a, dorsal view of entire animal; b, ventral view of male 

 reproductive system; c, upper jaw; d, lower jaw. 



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

 ardis and Dn. ileata at 10, 21; Dn. truncata at 88, 90 91; Dt.jalcata at 

 88-92 112; and E. internotalus at 88 and 90. 



Branchiobdellid associates include A. koronaeus and C. branchiophila 

 at stations 88-92, 112; C. fallax at 88, 89, 91, 92; C. holostoma at 10, 

 21; C. philadeljihica at all stations; and Xg. instabilius at 21. 



Remarks. — Xironodrilus formosus was associated with the riffle- 

 inhabiting Cambarus I. longulus in every locality that this worm oc- 

 curred and may be ecologically restricted to much the same habitat. 

 No conclusions as to host specificity should be drawn from this associa- 

 tion, however, for most of the range of Xd. formosus is outside that of 

 C. I. longulus. 



Genus Xironogiton Ellis, 1919 



Diagnosis.— Body terete anteriorly, depressed posteriorly ("tennis 

 racquet-shaped"); peristomium entire; posterior sucker ventral; 

 spermiducal gland long and tubular, deferent ducts entering near its 

 midlength, prostate absent; bursa large and asymmetrical; sper- 

 matheca very small. 



