170 NATURAL HISTORY BULLETIN 



rays interlocking; the marginal spinules are usually ten to 

 twelve on the larger paxillae. 



The under side of the inferomarginal plates has numerous 

 sharp, unequal secondary spines in two rows, and between these 

 numerous graded, rather acute, small subappressed spinules. 



The secondary spines on the under side of the inferomarginal 

 plates are of various sizes and acute; the surface spinules are 

 small, subappressed, not very acute. 



The adambulacral spines are well shown on plate xvi, fig. 2a, 

 in their usual state. Sometimes there are two small spines on the 

 adoral side of the large spine of the actinal face ; sometimes the 

 two are more unequal than in the figure. 



The special feature on which this variety is based is the pres- 

 ence of numerous well developed spinopaxillae on the dorsal sur- 

 face. 



Comparative Characters. 



The most prominent features for the recognition of this species 

 are the following : 



A. The presence of two incomplete rows of short spines on 

 the superomarginal plates, the two rows overlapping on the prox- 

 imal part of the ray; and the enlargement of the first pair of 

 plates and spines. These characters are also found in A. antil- 

 lensis and A. hraziliensis. 



B. The decided projection of the outer ends of the inferior 

 marginal plates, along the sides of rays, beyond the outline of 

 the upper plates, thus forming a sort of shelf, with a lateral 

 fasciolated lane above it. This character was even mentioned by 

 Gray (1840). 



C. The large size of one of the adambulacral spines of the 

 second series, but less so than in A. articulatus. Other charac- 

 ters of these spines, quite as important, need more careful scru- 

 tiny. 



D. The large size and flattened or lanceolate form of the in- 

 feromarginal spines, which stand two or three on a plate, the 

 proximal one larger; and the very spinulose condition of the 

 under side of these plates. 



According to the description of Miiller and Troschel, their 

 type of A. valenciennii had three ranges of adambulacral spines; 



