ASTEROIDEA OF NOKTH PACIFIC AND ADJACENT WATERS — FISHER. 



47 



Adambulacral plates about as wide as lon<^, with a rounded furrow margin, 

 but first two or tliree plates wider than long and with more angular margin. Arma- 

 ture consists of (1) a furrow series of four (more rareh* live) slender, rather long, 

 blmit cylindrical spinules, the two central being slightly the longest or the four 

 subequal; (2) on actinal surface are two or tliree longitudinal series of about four 

 similar spinules, wliich decrease in size toward outer etige of plate; third series 

 when present more irregular, its spinelets distinctly tapered, slenderer, shorter, and 

 sharper. Furrow spinelets usually bent back from furrow, and armature has a 

 decidedly crowded appearance. 



Mouth plates narrow, the free margin of each being longer than that adjacent 

 to first adambulacral, and the combined plates forming a salient angle into actinos- 

 tome. Margin of plate with a series of about 15 slender tapering spinules, decrea.sing 

 in length from inner to outer end of plate. About eight to ten of these arc more 

 regular and occupy the free actinostomial margin, the rest being adjacent to first 

 adambulacral plate, between which and the mouth plate there is a fairlj^ wide suture 

 furrow, and sometimes an incomplete, irregular, intermediate series is {)resent. 



Madreporic body situated about its own diameter from inner edge of supero- 

 marginal plates, fairly large, surrounded and partially obscured by large paxilla;; 

 striations deep, coarse, irregular, centrifugal. 



Superambulacral plates present, but small; one opposite each ambulacral plate 

 except the first plate and a few at the very tip of ray. 



Variations. — The variations exhibited by specimens of nearly ecjual size are 

 slight. The relative dimensions, with the niunber of superomarginal plates, are 

 listed below for several specimens: 



Measurements of Leptychaster pacificus. 



The paxillar area is slightly narrower in some examples than in others, and 

 the relative amount of inflation of the abactinal integument also changes the 

 external facies somewhat. 



Young. — There are three small specimens wliich seem to be the young of this 

 species; two from station 3223 have broader, more robust rays than a nearly cfjual- 

 sized individual from 4194. The characters of the latter are as follows: R = 9 mm.; 

 R = 4 mm.; R = 2.25 r. Breadth of ray at base, 5 mm.; supcromarginals, fifteen; 

 paxillie with three to five central and eight to ten peripheral spinelets; supcro- 

 marginals inconspicuous; abactinal integument inflated; furrow spinelets four 

 usually, the two central longest; actinal intermediate plates extending less than 

 one-third length of ray measured from interradial angle; terminal plates conspicuous. 

 One of the examples from station 3223 has the following characters: R = 10 mm.; 



