182 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



In some specimens of the less spinous subforma the abactinal spines are slender, 

 tapered, subacute, without, or with only a slightly swollen, subcapitate tip. They 

 stand usually singly on their plates and their collars of pedicellariae are generally 

 conspicuous. Plate 92, Figure 2, represents a specimen intermediate between 

 Figure 1 and < his w eak-spined variant (Monterey Bay). The giant specimen (pi. 91) 

 has tapered pointed spines and belongs on the border of brevispinus, as does Plate 93, 

 Figure 4. The latter has fewer and slightly stouter spines than specimen Plate 92, 

 Figure 1, and is an intermediate between the well-developed phase of brevispinus and 

 paucispinus. The loss of the adradial series of spines would transform this specimen 

 into one of forma paucispinus. This remark is true of the great specimen, Plate 91. 

 Compare it with Plate 90, Figure 2, a representative of the heavier spined subforma. 

 Both are from San Juan Islands, Wash. 



Superomarginal spines, one to three to a plate, are not of much value for diag- 

 nostic purposes. The number varies on different rays of the same specimen. Speci- 

 men, Plate 89, Figure 1, has two (sometimes one) on plates of proximal two-thirds 

 of ray and one on the distal third; Figure 2, the same; Plate 90, Figure 2, giant 

 specimen, has three sometimes with a small fourth, at base of ray, then two or three, 

 and finally one near tip; Plate 91, figure 1, giant specimen, two proximally and one 

 distally; Plate 92, Figure 1, irregularly two or one on a few proximal plates and one 

 on rest of series. Superomarginals are similar in size and form to the abactinals 

 but in some specimens are slightly gouge-shaped on outer side of tip. 



The inferomarginal and actinal spines are characteristic of the genus and present 

 no especial peculiarities. There are two clavate to subspatulate, usually externally 

 furrowed, inferomarginals, followed in a transverse series by three or four similar 

 actinals, all much stouter than the superomarginals. In well-developed specimens 

 the two outer actinals are generally a little larger than the inferomarginals. There 

 is considerable variation in the form of the spines and their robustness. In very large 

 specimens proximally the tips become flattened as if pinched while soft. A shallow 

 sulcus is normally present on the outer side in most of the specimens. (PI. 78, fig. 1.) 



Adambulacral spines slender, slightly tapered, round-tipped, forming a single 

 crowded series. Here and there a spine is squeezed a little in advance of its neighbors 

 on the furrow edge. Where the series bends upward toward the actinostome the 

 spines gradually lengthen and thicken, on the approach to the adoral carina, upon 

 which they are generally conspicuously stouter and longer. This carina is unusually 

 well developed and in mature specimens is composed of 12 to 15 pairs of conjoined 

 plates. (PI. 79, fig. 2a.) It curves upward to the actinostome, w r hich is sometimes 

 quite close to the dorsal wall of the well-arched disk. The first few plates of the 

 carina lack spines, although these same plates are spiniferous in young specimens. 

 In fully adult specimens the first adambulacral plate is conspicuously shorter than 

 the second; in young specimens they are subequal to or larger than the following 

 plates. 



The mouth plates widen with age and sometimes become somewhat distorted. 

 They are, as is usual in Pisaster, considerably broader than the narrow neck of the 

 adoral carina but there is little specifically characteristic. Ordinarily there are two 

 unequal flattened blunt marginal (actinostomial) spines and a longer and stouter, 



