ASPIDODIADEMA JACOBY] 27 



are less numerous in this species than in .1. microivbercuUdnm ; il also differs 

 from ii in having three or four ambulacra] plates (in the median region <>!' 

 the test) to each interambulacral plate, while there are no less than five or 

 six in A. microtubereulatum. The proportions of the spines to the tesl and the 

 general appearance recalls more A. tonsum, while the coloring when alive 

 is more thai of A. microtuberculatwn, with a lighl violel or grayish pink tesf 

 and the spines of the same tint bu1 lighter. The primary Bpines are slender, 

 as in A. tonsum, but they are more curved than in thai species. The abac- 

 tinal part of the tesl of A. anHllarum is more Battened | Echinostrephus-like) 

 than is the case in either of the species collected by the Challenger. 



The largest specimens of this species collected did not measure more than 

 1 3 mm. in diameter. 



In a specimen measuring 7.5 mm. in diameter, the anal system measured 

 3 mm., the abactinal 5 mm., and the actinal 3.75 mm. in diameter; the heigh I 

 of the tesl measured 3.75 mm. 



In a specimen measuring 11 mm. in diameter, the anal Bystem measured 

 3.6 mm., the abactinal 6.50 mm., and the actinal 5.50 mm. in diameter; the 

 height of the tesl measured 6 mm. 



' Aspidodiadema Jacobyi a \ 



Aspidodiadema Jacobyi A. Ao. Bull M C. /.. VIII., No 2, p. 7 1. 1880. 

 Cayman Brae, Lesser Antilles 9G to i".>7 fathoms. 



PI. JX . 



The largesl specimen of this species collected by the Blake measured 



'.','1 mm. in diameter. As in A. microtuberculalum, the primary spines are 



rather stout, curved, ami comparatively Bhort, thev are somewhat more 



closely packed than in thai species, from the greater number of primaries in 



the interambulacral areas, a specimen measuring 28 mm. in diameter having 

 LI: 12 primary tubercles. The miliaries are more distanl than in that spe- 

 cies, forming a bell of distincl irregularly arranged miliaries in the median 

 interambulacral space. We find in this species, as in A.ionsum, large pri- 

 mary ambulacra] tubercles, extending nearly to the abactinal Bystem; all 

 the largesl tubercles being placed above the median line of the test, and 

 gradually increasing in rize from thai point to the abactinal region, much 

 as they do in Echinostrephus. 



There are not more than three ambulacral plates to each interambulacral 

 plate. The miliaries extend in horizontal line- between the pores, ami form 



