ASTEROIDEA OF NOKTH PACIFIC AND ADJACENT WATERS FISHER. 195 



pair witli an ovoid form. On the broad inner triincatcly rounded end of combined 

 plates a series of seven spinelets, slifjbtly flattened and bluntly pointed, is {jjraduated 

 on either side from the median unpaired spine — there being; thus three spinelets to 

 each plate; on edge toward mouth of furrow are three or four smaller stum])y 

 spinelets graduated either way from the central. After an interval this series is 

 continued along margin adjacent to first adambulacral in five or six small papilliform 

 spinelets. About eight to ten sjiinelets stand on edge of median suture and five or 

 six, one of which may be enlarged, form an intermediate series. 



The postadanibulacral pedicellarite or fascioles are somewhat different from those 

 of type, and are intermediate in some respects between the latter and the ordinary 

 form. They extend about a third the length of furrow. At the base of the series 

 each consists of two or three flattened low jaws on either plate, forming a sort of 

 compound pedicellaria. One pedicellaria has a single long jaw on one plate and 

 opposing it two jaws, the whole occupying the entire width of the intermediate 

 plate. At the distal end of the series the pedicellaria; are single and like those of 

 type. It seems probable that as growth proceeds two opposing jaws develop, wliile 

 the others atrophy. The figures will give a better idea of these pedicellaria; than a 

 description w'ill. (PI. 57, fig. 7a.) 



The intermediate plates are armed with short papilliform spinelets, not so long 

 nor so slender as in tjrpe. There is usually one enlarged spinelct to each plate on 

 the disk. Papulse extend 0.6 length of R on radial area; not so far on sides, and are 

 lacking in a triangular interradial space. 



Young. — A specimen with R = 28 mm. is doubtfully referred to this species. It 

 has not yet developed the characteristic pedicellariae. The character of the spinula- 

 tion, armature of mouth plates and of adambulacral plates has led to the supposi- 

 tion that the specimen belongs here. 



Type.— Cat. No. 278S2, U.S.N.M. 



Type-locality. — Albatross station 3346, off Oregon, 786 fathoms, green mud. 



Distribution. — Bering Sea to Oregon, 786 to 1,064 fathoms. 



Specimens examined. — Five: the type; an immature specimen from station 3601, 

 Bering Sea, between St. George Island and the Bogoslof Islands, 1 ,044 fathoms, green 

 mud, fine sand; a j'oung specimen doubtfully referred to this species, station 3075, 

 ofl' Sea Lion Rock, Washington, 85!) fathoms, green mud ; two specimens from station 

 3788, off Cape Blanco, Oregon, 1,064 fathoms, green mud. 



Remarlcs. — This species is characterized bypostambulacral fascioles of a bivalved 

 form, which may consist, however, of multiple opposing jaws, and b}' the details of 

 abactinal, marginal, and adambulacral armature, as noted below in the comparison 

 with Ps. pectinifer, to which it is closely related. 



I liave two specimens of Ps. pectinifer Ludwig" from station 2807, Galapagos 

 Islands, 812 fathoms, globigerina ooze, coral mud. It is very evident that dissonus 

 bears the closest sort of relationship with pectinifer and probably has a continuous 

 distribution with it. No specimens of an intermediate character Or from interme- 

 diate localities are at hand however. 



<" Mem. Mu8. Comp. Zool., vol. 32, 1905, p. 106, pi. 7, figs. 34, 35. 



