GASTROTRICHA 627 



15 (14) Dorsal spines simple; i.e., without lateral barbs or points. . . . 16 



16 (17) Anterior region sharply set off from narrow "neck" region. 



Chaetonotus formosus Stokes 1887. 



Length 0.169 mm. Oral ring minutely beaded. Head three lobed. Dorsal and lateral 

 aspects of body covered with short, fine recurved spines with slight basal enlargements (but 

 without scales?). Spines all subequal, in length 0.0292 mm., or less. Trenton, New Jersey. 



No figure published. 



17 (16) Transition from anterior region to body gradual, not sharply marked 

 at any point 18 



1 8 (19) Head rounded Chaetonotus brevispinosus Zelinka 1889. 



Length of body 0.095 to 0.149 mm., of esophagus 0.0223 mm. 

 Spines somewhat curved, remarkably short, slightly larger poste- 

 riorly, arranged in eleven rows Head circular in front, with four 

 eye-spots. The only American species reported more than once. 

 Orono, Me., and Trenton, New Jersey. It is the C. larus of Stokes, 

 also of Fernald. 



FIG. 971. Chaetonotus brevispinosus in dorsal view, X 460, with spinose 

 scale more highly magnified. (After Zelinka.) 



19 (18) Head five lobed Chaetonotus acanthodes Stokes 1887. 



Length 0.1411 mm. Body covered with scales which bear each a 

 small supplementary scale; the latter in the anterior region possesses 

 a short, curved spine; just behind the middle of the body these termi- 

 nate in a cross row of larger spines. On each side near the caudal 

 processes are two larger curved spines. Trenton, New Jersey. 



FIG. 972. Posterior end of Chaetonotus acanthodes in dorsal view. 

 X about 570. (After Stokes.) 



