a. h. clark • the cbinoids op the mdi.\n ocean. 57 



11. — Key to the Genera of Stephanometrid.*:. 



a' Cirri long with more than 50 segments ; P, and Pj the longest, with about 25 

 short segments. 



OXYMETBA, p. i;}l. 



a cirri short, with less than 35 segments; the spine-hke lower pinnules have less 

 than 20 segments. 



STEPHANOMETRA, p. 132. 



12. — Key to the Genera of Pontiometrid^. 

 a' Size large ; all the pinnules present : P, on the outer arms by far the longest 

 pinnule ; more than 40 cirrus segments. 



pontiometra, u. 138. 



a* size small; P„ absent on the outer arms, P„ and P, on the inner ; Pj on the 

 inner arms the longest pinnule ; less than 40 cirrus segments. 



EPIMETRA, p. 138. 



13. — Key to the Genera op Mariametrid.^. 

 a' Disk plated; division series with a fine median carination ; sides of division 

 series and first two brachials with a tuberculous or finely spinous ornamen- 

 tation. 



mariajietra, p. 139. 



a' disk naked ; division series without any trace of a median carination ; sides of 

 division series and of the first two brachials without any ornamentation. 



b' cirri long, with 45 or more segments. 



selene.metra, p. 139 

 b cirri shorter, with fewer than 40 segments. 



dichrometra, p. 143. 



14. — Key to the Genera of Colobometrid.e. 

 a' P„ absent on all or nearly all of the arms. 



b' cirri long and comparatively slender with 24 or more segments, the more 

 proximal with spinous distal ends, the distal with paired dorsal spines ; 

 proximal pinnule segments slightly longer than the distal ; all the pinnules, 

 especially the proximal, stiffened, with very spinous distal ends to the 

 component segments ; none of the lower pinnules greatly longer than the 

 others ; ten arms. 



colobometra, p. 164. 



b* cirri short and stout with less than 30 segments which are usually subequal, 

 none with spinous distal ends, at least dorsally ; outer cirrus segments with 

 paired or tricuspid spines dorsally ; one or two of the proximal pinnules 

 enlarged and stiffened, but the remaining pinnules soft and delicate, 

 c' more than ten arms. 



CYLLOJIETRA, p. 156. 



