114 NATURAL HISTOEY BULLETIN 



Plate iii; figure 2. Young. Plate x; figures 1-16, 2-2/. Details. 



Disk broad more or less swollen; with evenly incurved mar- 

 gins, bordered by rather large, stout, marginal plates, and cov- 

 ered with numerous pretty regularly arranged polygonal plates, 

 which form the median radial rows. Rays rapidly tapered be- 

 coming slender distally, bordered by smaller convex plates, which 

 are in contact distally. All these plates are finely granulated 

 beneath a thin dermis that covers them, but does not entirely 

 conceal their outlines. 



The type of Perrier had the radii 32°^ and 80^; ratio, 1:2.5. 

 It had about 27 marginal plates, on each radial side. He men- 

 tioned others of larger size. One had the radii 53°^°^ and 156™™. 

 Another had them 33™™ and 131™™. These were from 151 to 150 

 fathoms. One taken by the Bahama Expedition had the larger 

 radius about 62™™ ; diameter 125™™, or about five inches. 



The inferomarginal plates, in the larger specimens, have a 

 marginal row of several small spines, or even more than one 

 row, on the interradial plates, when they become larger. 



Sometimes there is a ridge or line of coarser granules along 

 the superomarginal plates, on large specimens. 



The interactinal plates are numerous, extending to middle 

 of rays. They are polygonal, closely joined, granulated, and 

 with a thin outer dermis. Those next the jaws and adjacent 

 to the adambulacral plates bear a low, bivalve pedicellaria. 



The adambulacral plates have a furrow-series of about six 

 to eight small graded spines, the largest in the middle ; on the 

 actinal side there is another row of about three larger and short- 

 er spines. Very young specimens of this species have an appear- 

 ance quite unlike the adults, and may be mistaken for some other 

 species.^® 



This was taken by the Bahama Expedition on the Pourtales 

 Plateau, in 80 fathoms ("five inches in diameter"). Young ones 

 were taken in 60 fathoms, off Key West, station 26. It was 

 dredged by the Blake in 151 fathoms off St. Lucia; in 150 fath- 

 oms, off Guadeloupe ; 85 and 82 fathoms, off Barbados ; 73 fath- 

 oms, station 290, off Barbados (young) ; and at station 266, in 



18 In the Blake collection some young from station 243, in 82 fathoms 

 were labelled " Dorigona Mfurcata Perrier, MSS.," but other similar speci- 

 mens were correctly identified and labelled by Perrier. 



