644 

 45(i) 



FRESH-WATER BIOLOGY 



Without setae; pharynx with two chitinous jaws, dorsal and ven- 

 tral. Small leech-like, worms, parasitic or symbiotic, on 



crayfishes Family DISCODRILIDAE . . 46 



The family name Branchiobdellidae is preferred by some writers. 



46 (49) Two pairs of spermaries and two pairs of sperm-ducts in the fifth 

 and sixth post-cephalic somites 47 



47 (48) Without conspicuous dorsal appendages on post-cephalic somites. 



Bdellodrilus Moore 1895. 



B. philadelphicus (Leidy) and B. illuminatus (Moore) 

 resemble each other in having the anterior pair of nephridia 

 open to the exterior through a common pulsatile vesicle on 

 the mid-dorsal line of the third post-cephalic somite and in 

 having the dorsal and ventral jaws quite dissimilar. The 

 former has the head much broader than the anterior body 

 somite and enjoys a wide distribution in the eastern half of 

 the United States. The latter has nine pairs of conspicuous 

 lateral glands, the head narrower than the following somite and is less common. 



FIG. 994. Bdellodrilus philadel- 

 phicus. X Q. (After Moore.) 



B. pulcherrimus (Moore) and B. instabttis (Moore) re- 

 semble each other in having the anterior nephridia open 

 separately and in having the dorsal and ventral jaws simi- 

 lar. The former has all post-cephalic somites evidently 

 biannulate; alimentary canal straight; jaws small, each 

 bearing three teeth. The latter has biannulation con- 

 spicuous on only anterior four post-cephalic somites; ali- 

 mentary canal with transverse loop in seventh somite; 



and dark-brown jaws, each bearing four teeth. They have been described from North Carolina 



and Pennsylvania (Moore 1893). 



Under the name Cambarincola macrodonta, Ellis (1912) has described a species from Colorado 



which is closely allied to B. Philadelphia but which has the head narrower than the greatest 



width of the body and different shaped jaws. It also lacks the conspicuous glands of B. 



illurmnatus. 



FIG. 995. Bdellodrilus instabilis. 

 XQ. (After Moore.) 



48 (47) With conspicuous dorsal appendages on each of several post- 



cephalic somites Pterodrilus Moore 1894. 



P distichus Moore, with simple cylindrical dorsal append- 

 ages on each of post-cephalic somites II to VIII, and P. 

 alcicornus Moore, with dorsal appendages of complex form 

 on post- cephalic somites III and VIII and simple ones on 

 IV and V, have been described from crayfishes of eastern 

 United States (Moore 1894). 



Under the name Ceratodrilus thysanosomus, Hall (1914) 

 has described a species from Utah which resembles the 

 above described species of Pterodrilus closely, but has the 

 antero-dorsal border of the head furnished with a membran- 



,, ous border deeply incised to form four tentacular append- 



dorsal appendages are transverse bands with edges bearing six to eight points. 



49 (46) But one pair of spermaries and one pair of sperm-ducts and these 



in the fifth post-cephalic somite. 



Branchiobdella Odier 1823. 



B. americana Pierantoni has the prostomium entire and the jaws dissimilar. It has been 

 collected in Texas and North Carolina. B. tetrodonta Pierantoni has the prostomium divided 

 into dorsal and ventral lobes and the jaws similar. It is found in California (Pierantoni 1912). 



FIG. 996. Pterodrilus alcicornus. 

 X 5- (After Moore.) 



