204 NATURAL HISTORY BULLETIN 



It readily detaches its rays and therefore is seldom dredged 

 entire. It normally has five rays. 



The dorsal paxillae are stellate, much crowded, smallest in the 

 middle of the rays ; larger laterally. Each bears a circular mar- 

 ginal group of very slender spinules, one to three in the center, 

 and often, in adults, one to three blunt pedicellarige. 



Inferomarginal plates have, in the adults, a vertical row of 

 three long, tapering, acute spines, the upper ones largest. In the 

 young usually but two spines are present. 



The adambulacral plates have a transverse row of three rather 

 slender, sharp spines; the inner one smaller and recurved; the 

 middle one largest. A row of ovate, bilabiate pedicellarige oc- 

 curs between the inferomarginal and adambulacral plates. 



The type, as described by Perrier, was young ; it had the radii 

 5™"^ and 35"^°^ ; ratio, 1 :7. 



The inferomarginal plates are short, almost vertical, and bear 

 two or three long, sharp spines, besides their spinules. 



The dorsal paxillae are nearly alike, becoming more complex 

 toward the borders. Each has a rather short central spinule, sur- 

 rounded by six to ten longer, spaced, marginal spinules, scarcely 

 enlarged at the tip, and forming a simple stellate group, giving 

 the paxillar area a very uniform appearance. Madreporic plate 

 was concealed by the paxillae. 



On the actinal side there is a row of two-valved pedicellariae, 

 between the adambulacral and inferomarginal plates. 



Perrier (1884) mentions a much larger specimen, with radii 

 12™"^ and 115°^°^, and considers the presence of two-valved pedi- 

 cellariae distinctive of the species. 



The Bahama Expedition took, at station 63, in 85-95 fathoms, 

 a young specimen agreeing very closely with the type, in size 

 and most other characters. Its radii are 5.5°^°^ and 36™°^; ratio, 

 1 :6.54. It has two large, nearly equal, acute spines on the mar- 

 ginal plates, and occasionally a third, lower down. It also has a 

 series of small bivalve pedicellariae external to the adambulacral 

 plates, as in the type, so that there can scarcely be a doubt as to 

 its identity. 



It differs, however, from Perrier 's description in the character 

 of the dorsal paxillae. Instead of being nearly uniform, they are 

 decidedly diverse in size. The lateral row, on each side, con- 



