104 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



slightly swollen base, the distal portion being more finely grooved in small than in 

 fully grown examples. Carinals normally one to every plate; dorsolaterals much 

 more widely spaced, and in the equivalent of two or three longiseries, but not regu- 

 larly arranged, because the plates are not in definite longiseries. 



The abactinal skeleton of the ray consists of a close-meshed network of four- 

 lobed carinal and three to five, rarely six, lobed dorsolateral plates. The carinals 

 (with broader longitudinal than transverse lobes) are sometimes irregular in outline 

 where the series is distorted, but are directly imbricated in a definite, fairly regular, 

 line. The marginals are also directly imbricated, but the dorsolateral skeleton con- 

 sists of primary, spiniferous plates, connected by slender transverse, and very short 

 longitudinally oriented, intermediate ossicles. (Djakonov, pi. 22, fig. 6.) In each 

 mesh of the skeleton one, rarely two or three, groups of 7 to 15 papulae (even 

 more in largest specimens and fewer in young examples). 



Superomarginal spines one to a plate in a very regular longiseries at edge of 

 abactinal area. Separated from them by a regular series of papular areas, but by 

 usually less than their own length, is a double series of subequal inferomarginals. 

 The marginal spines are characteristically gouge-shaped and the tip is usually 

 slightly narrowed, subtruncate, or double pointed if the groove is deep. There is 

 no trace of an inferomarginal web, but each inferomarginal spine carries a basal 

 tuft of crossed pedicellariae. 



Actinal plates small, wedg?d between the inferomarginals and adambulacrals, 

 and entirely hidden by the thick integument. A regular series of actinal papular 

 areas, containing six or seven, or more, papulae. 



Adambulacral spines two, very slender, slightly tapered, the outer nearly as long 

 as inferomarginals, the inner usually a little shorter. Adoral carina consists of three 

 or four pairs of plates, the inner two usually each with one spine; first plate distinctly 

 longer than second. The specimen from Hong Kong has five pairs in the adoral carina. 



Mouth plates short, each with one suboral and two actinostomial spines; that 

 next to median suture is tapered, blunt, about as long as plate, the other quite small. 



Crossed pedicellariae (pi. 60, figs. 2, 2a) are often rather more tapered toward the 

 end than shown by figure and are characterized by unusually large terminal teeth 

 on either side of each jaw. These are stouter than in D. stichantha (Sladen). (PI. 

 60, figs, lc, leZ.) Average abactinal pedicellariae measure: Ayukawa, Japan, 0.45 

 mm.; Peter the Great Bay, 0.40 to 0.45 mm.; Hong Kong, 0.48, to 0.55 mm. 



The straight pedicellariae are characteristically slender, lanceolate and pointed. 

 Small ones, from 0.40 mm. to 1.0 mm. long, are fairly abundant on the abactinal, 

 lateral, and actinal surfaces, and on the adambulacral plates. Larger ones, 1.5 

 mm., are found in the intermarginal channels and actinal interradial regions. In 

 the larger specimen from Peter the Great Bay a very few of these pedicellariae show 

 one or two incipient teeth at end of jaw. (Djakonov, fig. 8.) 



Madreporic plate large, exposed, convex, one-third to one-fourth r in diameter, 

 and situated at about middle of r. 



Color in life: Entire actinal surface and all spines and wreaths of pedicellariae 

 yellowish white; skin of abactinal surface between the stoles of pedicellariae velvet 

 black, with dark gray papulae; madreporic plate, deep orange (Djakonov.) 



Type-locality. — Japan (northeast coast of Honshu). 



