SOME AQUATIC WORMS, ETC. 179 



13. CH^ETONOTTJS ACANTHOPHORUS. 



The superior surface of the head and neck and the 

 lateral body-margins are clothed with recurved prickles 

 or short spines, while the dorsal region proper bears 

 four rows of long thorns, each row curved towards the 

 head, and each formed of five unequally furcate spines, 

 with an additional one on both sides near the posterior 

 extremity. The spines rise from an enlarged base, so 

 that the animal is almost completely clothed in an armor 

 composed of these basal enlargements. 



14. ClLETONOTUS ENORMIS. 



The upper and lateral surfaces of the head and neck 

 are clothed with short, recurved prickles, which also ex- 

 tend along the ventro-lateral margins. The central and 

 posterior parts of the back bear thirteen posteriorly di- 

 rected, but only slightly curved, spines arranged in 

 transverse rows, with three in the first row, four in the 

 next following, two widely separated in the third, three 

 in the fourth, while the fifth series consists of a single 

 centrally located one. On each side near the posterior 

 margin are two long, conspicuous, and recurved thorns, 

 apparently belonging to the series of small spines fring- 

 ing the lateral body-margins. 



III. TURBELLARIA. 



The ciliated or Turbelldrian worms seem to prefer 

 the bottom of shallow ponds, probably because the food- 

 supply there is better and more easily obtained. They 

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