CIDARIS TRIBULOIDES. 253 



Cidaris tribuloides 



! Cidarilcs tribuloides Lame. 1816. An. s. Vert. 

 ! Cidaris tribuloides Bl. 1830. Zoopli. 



PI. P.; PI II f. 1-3; PI. II. f. 13. 



Genital plates somewhat rectangular; ocular large, triangular, with rounded 

 sides ; anal system pentagonal ; larger plates adjoining genital plates extend 

 little ways towards ocular, so as to separate the genital plates but slightly ; 

 whole abactinal system covered with miliary tubercles of nearly uniform size, 

 carrying small, flat, short secondary spines ; genital openings placed near outer 

 edge of the plates. Ambulacral zone with one outer row of miliary tuber- 

 cles separating it from the poriferous zones, and four rows of smaller milia- 

 ries, — two well defined, extending between them nearly the whole length of 

 ambulacra, and two exceedingly irregular ones of still smaller tubercles. 

 The two main rows of interambulacral tubercles are separated by a broad 

 median row of miliaries of nearly uniform size, slightly smaller on the me- 

 dian line, the miliaries round the scrobicular circle being but slightly larger. 

 The mamelon is small, with a moderate scrobicular circle. In large sj>eci- 

 mens there are three small miliary tubercles on each side of the perforated 

 scales of the actinal membrane. 



The primary spines are cylindrical, rather slender, sometimes slightly ta- 

 pering, in younger specimens slightly swollen near the lower extremity; their 

 coloration is light brown, violet tinged, often ringed with white and brown; the 

 granulation is quite close and compact. The secondary spines are broad, flat, 

 yellowish-green, tipped with brown ; the ambulacral miliary spines are elon- 

 gated, of the same color as the secondary ones, while in the interambulacral 

 zone they are gradually reduced to mere papilla? in a large part of the zones. 



Lutken has adopted for the common West India species the name of 

 C. metularia Lam., which he compares carefully with Cidaris tribuloides. 

 It is evident from his descriptions that his C. tribuloides is the C. metularia 

 Lam. ; he says himself that he may not have had the true C. tribuloides 

 Lam. From a direct comparison of the original specimens of Lamarck of 

 both these species in the Jardin des Plantes, there is no doubt that the 

 C. tribuloides of Lamarck is the common West India species for which the 

 name of C. annellata of Gray had been adopted in the Preliminary Report, 

 supposing Gray to have possessed, as far as could be judged from his descrip- 

 tions, the common littoral species of the Gulf of Mexico. Gray's originals 

 show that this was a mistake. The locality, however, of his C. annellata 



