9(J BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



to over one hundred on large paxilla>) slender and blunt, the most centrally situated 

 ones forming a flat-topped group, those about i)eripherv forming one or two irregular 

 tiers graduated in length (see pi. 52, fig. 36). Ten or eleven transverse rows of 

 paxilliB corresjiond to first four superomarginals. 



Unlike the two preceding species, the abactinal plates are not lobed, except 

 occasionally very slightly on mid-radial areas. (In D. nesiotes the abactinal plates 

 are circular, but placed more closely than in the present form.) Plates of the 

 regular lateral paxillar rows are subcircular, but the slight flange above the true 

 base of the plate or paxilla is frequently rather irregular. On the radial areas the 

 plates are more widely si)aced, uneven in contour, with slight traces of lobes some- 

 times, and without regularity in arrangsment. Papula^ distributed all over paxillar 

 area; in sixes about plates, but occasionally on the irregular median radial area 

 there are seven or eight. 



Marginal plates typical of genus; mferomarginals defining contour of ray, 

 forming a serrate edge. Superomarginals, thirty-five in number from interradial 

 line, are nearly ([uadrate except in interradial angle, where they are much wider than 

 lone. General surface is covered with slender and delicate, pointed spinelets about 

 the size of those on paxilht, forming a close nap very unlike either D. horealis or D. 

 eximius, but similar to D. 7iesiotfs. No specialized tubercles on superomarginals. 



Inferomarginals correspond to superomarginals, and do not encroach onto 

 actinal surface so much as in D. horealis. Surface is covered with delicate, imbri- 

 cating, narrow squamiform spinelets, which increase in size toward the outer aboral 

 edge of plate, there forming a tuft of five to seven small tapering spines, as in D. nesi- 

 otes. The abactinal end of plates is covered with slender spinelets like those of 

 superomarginals. The fasciolar furrows are wide and lined with delicate terete 

 spinelets. In proportion to length, the plates are much narrower (and are actually 

 so) than in eximius or horealis, but are sliorter and wider than in nesiotes. Com- 

 pared with the latter species, the fasciolar grooves are much wider and the 

 specialized ridge not so thick. 



Adambulacrul plates with a furrow series of seven very strongly compressed 

 bladelike spmes, their edges to furrow, and graduated toward either end of series. 

 These spines are much broader and thinner at tip than at base, the edge at tip being 

 rounded, laminar, and knifelike. On actinal surface are about ten to eighteen 

 slender, tapering or clavate spinelets decreasmg in size outward. Those nearest 

 furrow are subequal and largest, and commonly form a longitudinal series of five 

 to eight. 



Mouth plates elongate, the comijincd pair very tumid and the whole surface 

 bristling with sjiaced s])inclets similar to tiiose on actinal surface of adambulacrals. 

 Free margin with seven to nine compressed spines like those of adambulacrals, these 

 increasing in size toward the inner end of ])late. 



Actmal interradial areas fairly large, the intermediate plates about as numerous, 

 and intermediate areas as extensive on rays, as in horealis. The series adjacent to 

 adambulacrals extends 0.9 length of ray; the second, 0.6 to 0.65; the third, O.o; 

 the fourth, 0.15; a fifth extends to foi»rth inferomargmal ; between third adambu- 

 lacral and first inferomarginal is an interradial series of lune plates, the additional 

 plates being added rapidly between first and fourth inferomarginal. The fu-st row 



