A. H. CLARK : THE CRTNOIDS OF THE INDIAN OCEAN. 49 



gi cirri comparatively slender, with more than 25 segments, the 

 distal short and bearing dorsal spines; P, usually much enlarged 

 with stout segments, sometimes like P.^ but shorter ; genital 

 pinnules not expanded. „, 



(O) THALASSOMETRID^, p. 188. 



(Of. keys 5, 17.) 



g'^ cirri stout with usually less than 25 segments which are subequal 

 and do not develop dorsal spines distally ; P, and P^ longer and 

 more slender than the following, composed of very numerous short 

 segments; genital pinnules laterally expanded. 



(0) CHARITOMETRID^, p. 215. 



(Cf. keys 5, 18.) 



' at least the distal pinnules exceedingly slender, cylindrical, composed 



of much elongated segments; side and covering plates entirely absent 



or feebly developed and not visible in ordinary examination. 



f genital pinnules prismatic and longer than the distal ; cirri short , 



stout, with subequal segments which do not bear dorsal processes 



distally. 



(0) TROPIOMETRID^, p. 176. 



{Cf. key 15.) 



f* genital pinnules slender and cylindrical, of the same character as 

 the distal, but shorter. 



g' cirrus segments subequal, almost never longer than broad, bear- 

 ing a serrate transverse ridge or paired or tricuspid spines 

 dorsally; P.^ and sometimes also P.^ much enlarged, with spinous 

 processes on the distal ends of the segments. 



(O) COLOBOMETRID.^, p. 153. 



(Cf. keys 5, 14.) 



g^ some at least of the cirrus segments longer than broad; cirri 



smooth, carinate dorsally, or bearing single median dorsal spines. 



h' cirri robust, tenacious, the articulations not expanded; 



brachials exceedingly short, very much broader than lonw, 



discoidal ; P, shorter and weaker than P.^, with numerous short 



segments ; syzygies irregularly spaced and widely separated. 



(0) HIMEROMETRID^, p. 107. 



(Cf. keys 5, 10.) 



h'^ P, slender and delicate, usually flagellate, with much elongated 

 segments; cirri delicate, deciduous, with much expanded 

 articulations, at least in the proximal half; syzygies regularly 

 spaced and close together. 



(M) ANTEDONID^, p. 227. 



{Cf. keys 5, 19, 20.) 



