ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER 85 



laterals, and are unlike the carinals and inferomarginals. They form a zigzag aeries 

 and occasionally, as shown in the figure, one of the plates is four-lobed, as if con- 

 sisting of two fused plates. This type of superomarginal plate is present in Am- 

 pheraster hyperoncus (Clark), and A. atactus, especially distally, since in that species 

 the proximal plates are sometimes normally four-lobed. (See PI. 32, fig. 2.) If all 

 the superomarginal plates were regularly A and Y form there would be twice as 

 many as in the inferomarginal series, since it is only the alternate, Y-form, plates 

 which overlap the ascending lobe of the inferomarginals. 



The inferomarginals are normal, the lower lobe, which joins the adambulacral 

 plates, being very short. As shown in the figure, there are sometimes two intermediate 

 dorsolateral ossicles between the primary plates, and proximally there is a rather 

 long intermarginal ossicle. There is a quartet of enlarged superomarginals in the 

 interbrachium, the first pair lying outside the primary interradial plate; the second 

 pair is in line with the regular series and the lower ends overlie a pair of enlarged 

 inferomarginals. 



Intermarginal papular areas have proximally two papulae and the dorsolateral, 

 four or five in the smaller areas and about twice as many in the large. 



The skin is rather thick and pulpy, pretty well hiding the skeleton until dried. 

 The spinelets are small, solitary ; widely spaced, not very slender, tapered, bluntly 

 pointed, and terminally prickly; length, abactinal, 0.4 to 0.5 mm. long. The supero- 

 marginal are not different from the abactinal spines, but the solitary inferomarginal 

 spines are, as usual, much longer (1.7 mm. proximally), terete, slender, bluntly pointed, 

 a little stouter than the single, subequal, adambulacral spines. The latter are 

 always one to a plate, very slender, terete, blunt. There are 29 adambulacrals 

 to 10 proximal inferomarginals. The first adoral pair of adambulacrals do not meet 

 interradially. 



Oral plates narrow with a huge unguiculate pedicellaria as long as the plates on 

 the actinostomial end. There are two slender, slightly tapered, suboral spines. 



The straight pedicellariae are relatively huge, with broad spatulate jaws and 

 four or five curved tines. The proximal part of each jaw is narrowed as a rule. 

 They are very conspicuous and are scattered over the abactinal, marginal, and adam- 

 bulacral plates, a few overhanging the furrow, and four guard the actinostome. The 

 length is 1.1 to 1.25 mm. 



Crossed pedicellariae scattered, not so numerous as in A. atactus or A. hyperoncus. 

 Only one to three occur on the superomarginals and usually none on the inferomar- 

 ginals, except sporadically at very wide intervals; none on the adambulacrals. The 

 pedicellariae measure 0.30 to 0.36 mm. long and differ in form from those of hyper- 

 oncus and atactus, being much broader distally (as seen in profile), less tapered, with 

 fewer teeth than in atactus. 



Madreporic body small, near the margin, and attached to a very regularpenta- 

 gon of disk plates. 



Furrow fairly broad proximally, where the tube-feet are four-ranked; distally 

 they become biserial. The series of ambulacral pores are not nearly so straight as 

 in hyperoncus, but are decidedly zigzag proximally, though distally they straighten out. 

 The pores themselves are narrow elliptical while in hyperoncus they are broadly 

 elliptical. 



