A. H. CLARK : THE CRINOIDS OF THE INDIAN OCEAN. 45 



d' elements of the IBr series united by pseudo-syzygy , in external view 

 appearing just as if united by a true syzygy. 



{Q) ZYGOMETRID.E, p. 99. 



(Cf. keys 3—5 ; 9.) 



d^ elements of the IBr series united by synarthry. 



e' all the pinnules sharply triangular or prismatic, rather stout, the outer 

 with comparatively short segments which do not have swollen articula- 

 tions, their ambulacra bordered with well-developed side and covering 

 plates. 



f P, very delicate, flexible, and weak, the first two segments, 

 especially the former, greatly enlarged, the remainder very small 

 and squarish ; P.^ or P.^ much enlarged and stiffened, with elongated 

 segments ; elements of the division series thin dorsoventrally and 

 well separated, but sometimes with broad, more or less irregular, 

 ventrolateral processes; disk globose, compact, entirely enclosed 

 by a solid pavement of plates; muscular iossx on the articular faces 

 of the radials transversely linear. 



(0) CALOMETBID^, p. 177. 



(C/. keys 4, 5, 16.) 



f* P| without any special modification of the earlier segments, longer 



than, or resembling P.^, which resembles the succeeding pinnules; 



elements of the division series very deep dorsoventrally and sharply 



flattened laterally against their neighbours, without ventrolateral 



processes ; ventral surface of disk usually slightly concave, the sides 



not visible exteriorly ; disk studded with rounded calcareous plates 



which very rarely form a compact pavement ; muscular fossae on 



the articular faces of the radials very high, much higher than broad. 



g' cirri comparatively slender, often enormously elongated, with at 



least 25 segments, of which the distal are short and bear dorsal 



spines ; P, usually much enlarged, with stout segments, more 



rarely like Pj but slightly shorter; the genital pinnules are not 



expanded. 



(O) THALASSOMETRID.E, p. 188. 



(Cf. keys 4, 5, 17.) 



g* cirri stout, witii 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 expanded, protecting the genital 

 glands. 



(O) CHARITOMETRID.^, p. 215. 



(67. keys 4, 5, 18.) 



