254 NEW STARFISHES AND OPHIURANS—VERRILL. 



margin. The jaw-spines are slender, bnt three or four of them, at the 

 inner end of the iucnrved jaw, are much stouter than the rest; the 

 inner end of the jaw is prolonged inward and upward to an acute tip. 



This species is more closely allied to P. intermedius, Sladen, than to 

 any other species hitherto found oft' our coast. The latter has a smaller 

 disk, with the upper marginal plates projecting farther inward, thus 

 producing a broader margin and a narrower paxillary area along the 

 rays; its paxillie are smaller in speciuiens of the same size, more closely 

 crowded, and have the granules closely crowded together and angular, 

 the whole set forming a compact group, in which the marginal papillie 

 differ but little from the other granules. The upper marginal plates 

 are also much more closely and uniformly covered with granules, 

 which are so closely crowded together that they have a polygonal form, 

 especially on the upper portion of the plates, where they are smaller 

 than below. 



The lower marginal plates are also much more densely spinulated and 

 usually have but a single series of a few enlarged, median spinules, not 

 much larger than the rest, while the others are small, short, appressed, 

 crowded, and more or less closely imbricated; those on the lower part 

 of the plate are ovate and often subacute, while those at the upper end 

 of the plate become polygonal and granule like, and similar to those of 

 the upper plates ; their marginal papilhe are also characteristic, being 

 short, thick, angular, and very closely arranged in a regular row. The 

 interradial areas are relatively smaller, with more numerous, closer, and 

 smaller, shorter spinules, of which one, a little larger and longer, 

 usually occupies the center of each plate, while the others mostly 

 surround the margin and form distinct fascioles between most of the 

 plates in our numerous specimens (though, according to Sladen, no 

 fascioles existed in his specimens). The adambulacral spines are more 

 equal and form more regular and more prominent groups, the outer 

 marginal ones being more numerous and forming a more regular, diver- 

 gent, curved series, while the central ones form a group of five to seven 

 larger ones, about equal in length and size to the furrow series; the 

 latter form an angular group of seven to nine, which are usually 

 strongly transversely compressed and blunt. The jaw-spines are much 

 more numerous, stouter, and more crowded; they form a conspicuous, 

 broad-ovate group on the actinal surface of each jaw, with the narrow 

 suture in the middle. 



This species has a striking resemblance to Isaster bairdii in form 

 and in the character of the abactinal region and upper marginal plates. 

 The disk, however, is somewhat smaller and the rays relatively longer. 

 The paxilhie are a little smaller and the granulations somewhat finer in 

 specimens of the same size; moreover, their marginal granules are finer 

 instead of coarser, as in the latter. However, the strong spinulation 

 of the lower surface and inferior marginal plates is widely dift'erent 

 from the even granulation of I. bairdii. The angular groups of adam- 



