152 BULLETIN 100, unit^:d states national museum. 



DIPSACASTER DIAPHORLS Fisher. 



Pl.'ite 12. fig. 3; plate 28, fig. 2; plate 29, fig. 2; plate 31, fig. 1; plate 41, 



figs. 3, 3a-c. 



J>i/i-s(i('ish r dill j)li(iriis Fishek, ]913«, p. G22. 



Diagnosis. — Similar in form to D. sladeni, but ditfering in having 

 short, thick, chivate, or siibterete thorny paxillar spinelets, more 

 niiiiierous adanibiilacral spinnles, a small madreporic body and less 

 conspicuous marginal spinules; all the shorter spines and spinelets 

 thorny; paxillae with 20 to '2o spinelets; furrow spines 8 or 9, very 

 slender, pointed, slightly compressed; subambulacral spinules, 15 

 to 20 in series or forming a sort of rosettelike group on the convex 

 surface of plate; madreporic body small. Rays rather slender, 

 disk large, interbrachia abruptly rounded. R=31 mm., r=10 mm., 

 11=3 r-f- ; breadth of ray at base, 11.5 nmi. 



Description. — Paxillar area compact. Paxillae comparatively 

 large, largest laterally at base of ray and adjacent interradial regions 

 of disk; smaller in center of disk. Pedicels rather short, crowned by 

 'a capitate group of 20 to 25 thick clavate or cylindrical round-tipped 

 minutely' thorny spinelets, about as long as the pedicels, and rela- 

 ti\ely fewer and thicker than usual in this genus. Abactinal plates 

 relati\ely large and close-set, those of the disk roundish, with some- 

 times an indication of lobing, becoming broadly elliptical on the 

 radial line and s(mie\vhat four-sided or subelliptical laterally. The 

 ])apulae are absent from center of disk and midradial line, but this 

 is very likely due to the small size of specimens. In the specimen 

 from station 5123 many of the paxillae have the spinelets closely 

 appressed and witli slightly larger tips, resembling a simple pedi- 

 cellatian ajijjaratus. 



Superomarglnals 23, abactinal in position, nearly square except in 

 the interbrachia. and covered with slightly spaced spinelets similar to 

 those of the ])axil]ae, though a trifle stouter on the exposed median 

 area of the phite. Fascioles wide and moderately deep. Terminal 

 plate broado!' than long, saddle-shaped, with a wide, deep notch 

 toward the paxillar area. 



InlViomarginals extending laterally beyond the superomarglnals 

 and corresponding to them, plate for plate; in w^idth about equaling 

 the length of 2 with intervening fasciole. Plates covered with 

 spaced, appressed, slender, sharp, sometimes flattened and squami- 

 form spinelets, becoming a tuft of longer spinules on the outer 

 end. Two or three of these are largei' than the rest, arranged in a 

 transverse series and similar to the lateral spines of D. sJadcni, 

 though less conspicuous. 



Actinal interradial areas only moderately large; the plates in a 

 larger and more mature specimen would probably extend farther 



