176 NATURAL HISTORY BULLETIN 



the two rows a long flat acute spine nearly as long as the breadth 

 of the plate, so that this margin seems to bear three spines, in- 

 stead of the two marginals found in A. antillensis. 



The adambulacral plates have an inner marginal series of 

 three spines, in which the median is larger than the others, re- 

 curved, and flattened; on the actinal side there is a median, 

 large, conical, acute spine, and two others, at one side, about 

 half as long ; exterior to these are other small spines, in a row or 

 irregularly placed. 



Off Bahia, Brazil, 7 to 20 fathoms, and at Fernando Noronha 

 (Sladen). Bay of Rio de Janeiro, common, (C. F, Hartt; R. 

 Rathbun) . 



Sladen (1859) in his analytical table, puts this down as hav- 

 ing three inferomarginal spines. This appears to be due to the 

 presence of two secondary spines, belonging to the two central 

 rows, standing one on each side, and a little below, the single 

 large marginal spine. When the second true marginal spine, 

 of smaller size, appears it is on the same level or a little above 

 the large spine and on the adoral edge of the plate. 



This is the only species from the West Atlantic, known to me, 

 that has, normally or commonly, only one true inferomarginal 

 spine. This is, therefore, a good diagnostic character. Various 

 foreign species have a single spine, normally. 



Another good diagnostic character is the openly subspinulose 

 covering of the superomarginal plates, while all the otherwise 

 similar species have them closely granulated. 



AsTROPECTEN coMPTUs Vcrrill, sp. nov. 



Pla.te xii; figures 3-3c. Details. Type. Plate xxii; figure 1. 



Type. 



Rays rather stout, elongated ; the largest adult has about 48 to 

 50 spineless, evenly granulated, transversely rectangular super- 

 omarginal plates, proximally about one-third as wide as the 

 width of paxillar area of the ray, and encroaching on the upper 

 side so as to form a conspicuous and somewhat raised border. 



Radii of the largest specimen, 18™™ and 95™™ ; ratio, 1 :5.3 ; 

 breadth of ray at base, minus spines, 19™™ ; breadth of paxillar 

 area, 11™™ at second plate. Radii of the type specimen (No. 



