182 NATURAL HISTORY BULLETIN 



Radii of one of tlie larger are 10""™ and 44"^^ ; ratio, 1 :4.4. An- 

 other has them lO™"* and SS"^"" ; ratio, 1 :3.8. Another, 8""™ and 

 32°"" ; ratio, 1 :4. The margin is narrow and not very thick, 

 owing to the smallness of the marginal plates. The dorsal paxil- 

 lar area is relatively wide. 



The paxillae are small, nearly equal and even, regularly stel- 

 late, arranged in obliquely transverse rows. Two rows usually 

 correspond to each superomarginal. In the proximal interradial 

 region there may be ten paxillas in a row from the margin to the 

 median radial line; opposite the eighth pair of plates there are 

 about six; toward the tips of the rays the rows are indistinct. 

 The larger proximal paxillae may have eight to ten spinules 

 around the margin and one, or less often two, in the center. At 

 about the middle of the rays the larger ones have six to eight 

 marginal and a single small central one. The spinules are slen- 

 der, not very long, obtuse, or slightly capitate, all nearly equal. 

 The paxillar columns are rather high and slender, with round or 

 elliptical convex tops. They are in close contact by their bases 

 along the median line, but elsewhere have isolated papular pores 

 between them. 



The superomarginal plates are rather small, higher than long, 

 proximally, with the outer side nearly vertical and the upper 

 end narrow but prominent. Their sutures are deep and finely 

 fa&cioled. There are about thirty-two plates on each side of a 

 ray, in the larger specimens. 



The superomarginal plates are regularly covered with small, 

 short and very slender spaced spinules, usually as fine and some- 

 times finer than those of the dorsal paxillse ; those in the lateral 

 fascioles are still finer and very numerous. Each plate usually 

 bears a small, rather short, tapered, acute spine on the most 

 convex part of the upper side ; these are larger proximally, grad- 

 ually decreasing distally, and becoming very small on disappear- 

 ing toward the tips of the rays. They are usually in a very 

 regular row, but some are often lacking and sometimes there is 

 a smaller one (sometimes two) close beside the larger one. 



The inferomarginal plates correspond in number and length 

 with the upper ones Their fascioled suture are deep and some- 

 what oblique proximally, becoming decidedly oblique distally. 

 These plates are prolonged to the adambulacrals and are but little 



