488 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



spines between the adambulacral spines and the inferomarginal 

 spines (of which there are 2). On the abactinal surface, between 

 the 2 siiperomarginal series, are 3 series of spines proximally, and 

 only 1 (the carina!), distally; only 1 kind of major pedicellariae 

 present, slender and lanceolate in form; rays pentagonal in section, 

 the width of the lateral face proximally being about two-thirds that 

 of either dorsal face (between superomarginal and carinal row of 

 spines) while distally all four are nearly equal; disk very small, 

 sunken below the dorsal surface of rays ; rays constricted at basp. 



Description. — Plates arranged as follows: A carinal series, and on 

 the dorsolateral angle of the ray a superomarginal, alternate plates 

 of each series bearing a conical sharp spine; nearly midway between 

 the two, a series of usually 3-lobed, much smaller, adradial plates, 

 bearing somewhat irregularly a small conical spine on the proximal 

 half of ray, and extending nearly to the tip of ray. Frequently 

 they are so arranged that the alternate plates are connected with the 

 carinals either directly by a dorsal lobe or by a short elliptical inter- 

 mediate ossicle, while the other plates are joined to the superomar- 

 ginals by a longer intermediate ossicle. Actinolateral border of 

 ray very abrupt and formed by the inferomarginals, each bearing 2 

 slightly tapering flattened truncate or blunt spines in an oblique 

 series, the outer a little longer, and above and adorad to the other. 

 Extending two-thirds the length of the ray, between the inferomar- 

 ginals and adambulacrals is a single series of small plates which are 

 separated one from another by a papular area equal to their own 

 length and extending two-thirds the length of the ray. For a third 

 or a half the length of ray (depending upon size of specimen) each 

 intermediate plate bears a small acicular spine about three-fourths 

 the length of the outer adambulacral spine. The base of the inner- 

 most marginal spine is spaced from the outer furrow spine about 

 the length of the latter. 



The abactinal and superomarginal spines are surrounded by a 

 basal sheath closely crowded with small forcipiform pedicellariae, 

 while only the upper side of the upper inferomarginal spine is so 

 provided — there being but a half circle of pedicellariae. These pedi- 

 cellariae are about 0.35 mm. long, have about 5 lateral teeth and a 

 broad terminal portion armed with many small teeth. There is but 

 one sort of major pedicellariae — in form, slender, lanceolate, and 

 pointed — scattered rather numerously on the abactinal and actinal 

 surface. There are 2 series of papular areas between the carinal 

 and each superomarginal series of plates, each with about 10 to 15 

 papulae; an intermarginal series on each side with 5 to 8 papulae 

 to the area; and an actinal series alternating with the actinal inter- 



