246 NEW STARFISHES AND OPRIURANS—VFAiRILL. vol.xvii. 



the two forms described by Sladen from oft' the American coast are 

 probably both identical with that described by me. 



This species varies considerably in several details of its structnre, 

 according to its age. ^oue of Sladen's specimens were full grown 

 (largest size given is 74 mm. in diameter). Moreover there is often 

 considerable variation in specimens of the same size and from the same 

 locality, in the size of the disk, number, size, and arrangement of the 

 spires on the marginal plates, etc. Some few examples have the disk 

 at least one-third broader than others having the same length of rays, 

 and such specimens naturally have large inferior interradial areas, 

 with the plates more numerous than usual, as many as twenty to twenty- 

 five being present in some cases. The papulie often extend out on the 

 rays, in large examples, as far as the fifth pair of marginal plates ; they 

 cease sooner in the median line than to either side of it. They are often 

 present on the central area of the disk, among the large primary spines. 

 Theactinal and adambulacral spines on the largest specimens are more 

 numerous and longer than Sladen's descriptions indicate, but the half- 

 grown specimens agree well with his examples, in most respects. 



The pectinate pedicellarisie described by Sladen as characteristic of 

 P. armatus are commonly lacking entirely on our specimens, or exist 

 only in very small numbers. The dorsal plates of the rays are rounded 

 and ovate, unequal, and most commonly isolated in the integument. 

 They usually bear only a single, small, slender, acute spine, rarely two. 

 The large disk-spines are variable in number and length, but they are 

 always restricted to the central area of the disk, and the largest are 

 borne on the primary i)lates. The large single spines on the odd inter- 

 radial marginal plates are usually long, tapered, acute, and distinctly 

 larger and longer than those on the disk. The lower marginal plates 

 generally bear, in large specimens, one large, primary, acute spine, and 

 one or two, rarely three, secondary ones below it, besides several small, 

 slender, divergent, rough spinelets scattered around their bases. The 

 adambulacral plates, in such specimens, generally have two or three long, 

 slender, rough spines on the actinal side, besides several small, slender, 

 spinelets on the outer margin; the angular and salient inner margin 

 usually bears about seven slender spines in a V-'^baped group. 



I have seen a few regular four-rayed specimens, and also one pecul- 

 iar monstrosity, in which a small supplementary ray buds out from the 

 side of the regular ray, near the base. This species occurred at many 

 stations in 721 to 2021 fatlioms. 



PONTASTERIN^, ucw Subfamily. 



Rays long; disk of moderate size, Papuhe arranged in a group at 

 the base of each ray, aiul sometimes on the disk. Dorsal surface cov- 

 ered with spinopaxilke and protopaxilhe. Marginal plates all paired, 

 usually spiniferous. Pedicellariit often present, mostly compound, two 



