Prof. F. J, Bell on u new Species o/'Eveehinus. 403 



LIII. — Description of a neia Species o/Evechinus. 

 Bj F. Jeffeey Bell, M,A. 



[Pkte XVIL figs. 7 & a] 



There lias for some time been known^ to me a form of the 

 genus Evechinus which did not appear to be the same as E. 

 chloroticus ; as, however, the two specimens in the collection 

 of the British Museum are of small size, and as the habitat 

 is unknown, I have for several years delayed publishing the 

 description in the hope that fresh material would come to 

 hand. I now reverse the policy, in the hope that by directing 

 attention to this undescribed form further information will be 

 supplied by those who may possibly have examples of it 

 under their care, or in their possession. 



Evechinus rarituhercidatus. 



This species may be distinguished from E. chloroticus by 

 tbe following characters : — the primary tubercles are less 

 numerous and less closely packed, there is a great reduction 

 in the number of tubercles found in the interambulacral areas, 

 the actinostome, abactinal area, and anal area are propor- 

 tionately larger, and the poriferous zone is narrower. 



Test discoidai, rather flattened, blackish brown, the promi- 

 nent primary tubercles of the ambulacral areas faintly greenish. 

 Madreporic plate large ; two oculars touch the anal border ; 

 one large and distinct tubercle on the ordinary genital plates 

 and a few small tubercles on the oculars. Actinal cuts dis- 

 tinct but not deep; actinostome rather large. 



The primary tubercles of the ambulacral area, which are 

 largest at the ambitus, diminish in size more rapidly below 

 than above this line. In a test of rather more than forty 

 millim. in width about fourteen may be counted in each row • 

 the tubercle stands rather towards the ambulacral edge of the 

 plate and has a circlet of railiaries around its base ; between 

 the two rows of primary tubercles we find at and below the 

 ambitus two rows of secondary tubercles, one on either side 

 of the middle line ; above the ambitus these rows rapidly 

 become obscure. On the outer side of the primary tubercles 

 we find an irregular row of small tubercles, which are largest 

 just below the ambitus and quite lost halfway up tlie abac- 

 tinal side of the test ; of these one on each plate is distinctly 

 larger than the rest. 



In the interambulacral areas, on the actinal face of the test, 

 we find two rows of ordinary primary tubercles, rather closely 



