70 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



strongly granulate; lower side of arms showing two ranges of plates 

 on each side of the avenue, the outer range composed of strong 

 hexagonal plates, with an inner range of smaller ones alternating, 

 the latter usually covered by tufts of spines; a lai^e pentagonal plate 

 mserted at the base of the arms, on the lower side. 



''In this species, the arms are about twice as long as the width of 

 the disk. There are about 15 or 16 plates in each range from the 

 base to the apex of the arms. The range of the plates margining 

 the avenue are usually not visible, the whole being covered by the 

 short spines, which also partially fill the avenue." 



In 1870 Hall added the following important observations: 



"I have distinctly recognized the two ranges, marginal and 

 adambulacral plates; but the inner ones are not shown in the figure 

 as they should have been, while the large plate at the axil of the ray 

 (though the adjacent small oral plates of the inner range are not 

 seen) is evidently part of an incomplete series, and clearly belongs 

 to the marginal range. 



"The genus Palxaster has two ranges of plates on each side of the 

 ambulacral groove; marginal and adambulacral plates on the lower 

 side, besides ambulacral or poral plates. The upper or dorsal side 

 has three or more ranges of plates." 



Emended description. — Measurements: 11=18 mm., r=5 mm. 

 Width of ray at base 5 mm. 



Kays long, slender, tapering slowly; abactinally strongly convex 

 and longitudinally ridged; flat actinally. Disk comparatively large, 

 stronglj' convex and probably abruptly elevated above the rays 

 abactinally. There are no interbrachial arcs, but the five axillaiy 

 marginal plates occupy the axils and are also partially visible 

 abactinally. 



Abactinal area of rays consisting of 4 columns of large, tliick, 

 convex plates. These are the supra- and inframarginal columns. 

 The supramargmal plates of each ray are distally in contact with 

 one another along the mid-Hne, but proximally they are forced more 

 and more apart by a series of small, irregular, accessory plates. In 

 the center of the disk there is a small, convex disk plate around which 

 are situated radially 5 other small ossicles, all of which are sepa- 

 rated from each other apparently by a considerable number of minute 

 intercalary pieces. Just inside of the axils are 5 large, subtriangular, 

 interradial plates and adjoining these directly are 10 large and con- 

 spicuous ones, the proximal plates of the supramarginal columns. 

 In each column there are about 13 plates, not counting the proximal 

 piece. Between all of the' larger plates of the disk and for two- 

 thirds the length of the rays between the supramargmals, there are 

 numerous small, convex, iiTegularly shaped, accessory plates. All 



