SOME AQUATIC WORMS, ETC. 193 



formation. They may measure half an inch or more in 

 length. 



6. AULO'PHOEUS (Fig. 138). 



The posterior extremity is not wider than the width 

 of the body, and the two finger -like appendages are 

 straight or slightly curved. They are blunt, and covered 

 with short stiff hairs. The worm usually builds a tubu- 

 lar sheath of various fragments and floating particles, in 

 which it lives, but to the walls of which it is not ad- 

 herent, as it frequently doubles on itself, glides through 

 the tube, and thus reverses its position. It 

 moves by jerks, " alternately extending the 

 fore part of the body and projecting the FI^. iss. POS- 



T i r> i ,> i t i i , tcriorextrem- 



podal fascicles forward, and hooking into jt yofanAui6- 

 the surface on which it is creeping, and P horu8 

 then contracting the fore part of the body and drag- 

 ging along the back part enclosed within the tube."* 

 It often helps itself along by clinging to the slide by 

 its protruded throat or pharynx. The podal spines vary 

 in number from five to nine in each cluster. The 

 fascicles of bristles are each accompanied by from one 

 to three rudimentary spines, which are nearly straight, 

 and end in a broadened, spade-like expansion. The blood 

 is red. 



7. STREPHURIS (Fig. 139). 



The podal spines and bristles are arranged alternately 

 with each other, as in Fig. 139, and together form a single 



* Dr. Leidy, in the American Naturalist, June, 1880. 



