28 BULLETIN 7(5, UNITED STATES NATIONAL MUSEUM 



form, and the relative size of the supero and infero marginals. The latter are more 

 variable inter s< than the former. They are usually a trifle to decidedly larger than 

 the Buperomarginais, varying from cylindrical to a subspatulate form, almost always 

 swollen toward the tip. which is rounded or truncate, or slightly bent upward. The 

 actinals are similar, but a little less heavy. The adambulacral spines ordinarily 

 alternate <me and two, and are terete, much slenderer than the actinals, and less 

 variable as to form. The inner or furrow spine is slenderer than the outer, while 

 the alternate single spine is about intermediate in size. One specimen, on the 

 proximal half of ray, has two spines on nearly all the plates. The largest specimen 

 in the collection, station A442, with K 73 nun., has only one adambulacral spine to a 

 plate. Crossed pedicellariae are very numerous. 



The crossed pedicellariae are more numerous and larger than in the forma 

 arctica (measuring about 0.27 mm. in length), but in this abundance there is consid- 

 erable latitude. The abactinal spines, however, are provided with rather thick 

 -heaths which usually reach nearly to the tip, and are there beset with one or, on 

 the dorsolateral regions, two circles of pedicellariae, while the marginals may have 

 three or four circles. On the inferomarginals there are often only half circles, and 

 the actinals regularly have only half circles on the outer side. For different varia- 

 tions see Plate 14, Figures 1, 2; Plate 15, Figures 3 to 5; Plate 16, Figures 2 to 6: 



Unguiculate straight pedicellariae are scattered rather sparingly over the abac- 

 tinal surface but are fairly numerous and somewhat larger in the intermarginal 

 and actinal channels, and in the interbrachial channel. Considerably smaller 

 pedicellariae, with rather narrower jaws and smaller teeth are found sparingly on 

 the proximal furrow spines. But 27 examples from station 3559, 39 fathoms, gray 

 sand, vicinity of Pribilof Islands, while exhibiting individual variation, have these 

 straight pedicellariae of the furrow spines much more numerously represented, 

 even in -mall specimens. Straight pedicellariae are also more numerous on the 

 body surface. The same is true of station 3543. (See pi. 9, figs. 9, 10, 11.) While 

 the dimensions vary a good deal, an abactinal pedicellaria of a large specimen is about 

 ii .'.» mm. long, an axillary 1 mm., a suboral 0.6 mm., and a furrow 0.5 mm. 



One of the specimens from station 3559 (pi. 15, fig. 1), intermediate with forma 



co, K •"><; mm., is remarkable for having the superomarginal spines in a vertical 

 arcuate series of generally three, or two on the distal third of the ray. The lowest 

 -.pine stands on the descending lobe of the plate and would be classed as one of an 

 intermarginal series which extends two-thirds or three-fourths the length of the 

 ray. This gives a very spiny aspect to the lateral face of the robust ray. The 

 pines <»f the radial region are coarse and abnormally crowded, the adambulacral 

 are heavier than usual and clavate, truncate, while the crossed pedicellariae 



unusually numerous. The other specimens have only a single superomarginal 

 spine and are -lender rayed. 



8teiwn .3294, Bristol Bay, 80 fathoms, black gravel, July 18, 1890.— The greater 

 [lumber of the 14 large specimens have the abactinal spines more widely spaced than is 

 usual although the appearance is accentuated by the turgid rays (swollen by large 

 gonads). The relatively lew straight pedicellariae are slenderer and lack teeth as a 

 rule. These, however, are present on pedicellariae from specimens taken at 3295, 

 11] fathoms, line gray sand, same general locality. The more sparsely spined 



