136 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



lip, which as seen from the side, extends further down the jaw. The pedicellariae of 

 the smallest specimen (station 2856, R 33 mm.) are about two-thirds the length of 

 the largest. (PL 60, figs. 46, 4c, U.) 



Straight pedicellariae very numerous. (PL 61, figs. la-Id; pi. 62, figs. 2, 2a.) 

 The common sort is somewhat spatulate in form with usually two or three curved 

 claws which interlock with those of the opposite valve. Sometimes only one tooth 

 meets two, or two interlock with three. Such pedicellariae are scattered liberally 

 over the dorsal surface; in the intermarginal and actinal channels; between the infero- 

 marginal plates; in the actinal interradial area, and on the mouth plates. They 

 have longer claws than the very much less numerous corresponding pedicellariae of 

 nanimensis, and in length measure from 1.2 to 2.25 mm., the largest being in the 

 actinal interradial channel. Besides these, there are a few smaller wedge-shaped or 

 subconical, toothless abactinal pedicellariae. Along the furrow at the base of the 

 inner spines are numerous lanceolate, long-peduncled pedicellariae, as many as four 

 or five to a plate in some examples from Bering Sea and the Kamchatkan region. 

 A representative example measures 1.17 mm. long by 0.40 broad at the base of valves. 

 The tips of the jaws are sometimes slightly crossed and near and on the mouth plates 

 are forms intermediate with the unguiculate variety. In nanimensis the furrow 

 pedicellariae are very few. 



Madreporic body variable in size, medium to large, with fine radiating striae. 



Color in alcohol, yellowish brown to dark gray; tips of abactinal spines blackish. 



Variations. — Since the race ranges from the Gulf of Alaska to Saghalien and from 

 low tide, in some localities, to 93 fathoms (off Unalaska), it is not surprising that 

 there should be considerable variation. What might be called the average or mean 

 for the species however is found in all parts of the range, with only trifling differ- 

 ences, and the most striking variations are local — at least so far as known. 



Perhaps the most conspicuous variation is in the stoutness of the rays. A 

 specimen with R 115 mm. from station 4795 has relatively thick, short rays, their 

 breadth at the widest part being about one-fifth length of ray measured on the side. 

 This specimen has very large gonads. In sharp contrast are three specimens from 

 station 2856, Gulf of Alaska, 6S fathoms, which have slender rays. In one of these 

 (with R 130 mm.) the greatest width of the ray is only one-eighth of the length (there 

 being only a rudimentary gonad). In average specimens the ra3 T s are six to seven 

 times as long as the greatest breadth. 



There is some variation in the form and number of unguiculate straight pedicel- 

 lariae, and they are relatively larger upon small than upon big specimens. On the 

 former they often exceed the spines in length, but the reverse is true for large examples. 

 The lanceolate pointed pedunculate pedicellariae of the ambulacra! margin are 

 usually numerous, but not always so. The depth and number of vertical furrows at 

 the tip of the dorsal and marginal spines is quite variable, but the channels are usually 

 relatively few and deep. As noted in the description, the inferomarginal spines are 

 often gouge-shaped in full-grown examples. 



The most striking departure from the normal for the race is exhibited by a large 

 example (R 220 mm.) taken by the Vega Expedition, August 14, 1879, at station 

 1075, Bering Island, 65 fathoms, clayey sand. The proximal superomarginal plates 

 carry a vertical row of two or three spines, rather slenderer than usual, while beyond 

 the middle of ray there is practically never but one spine. The specimen was prob- 

 ably quite old as the abactinal spines are very numerous — 20 or more between the 



