. Fresh-water biology. Freshwater biology. 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 pa
. Fresh-water biology. Freshwater biology. 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 Une 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 9. (After Moore.) B. pulcherrimus (Moore) and B. instabilis (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, Elhs (1912) has described a species from Colorado winch is closely alhed to B. philadelphicus 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. lUummatus. Fig. 995. Bdellodrilus instabilis. X
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