202 Bulletin American Museum of Natural History. [Vol. XXXII, 



Between the median radial series of plates and the superomarginals there is only a 

 single, somewhat irregular series of abactinal plates. There are here and there 

 indications of a second series but they are very scattered. The inferomarginals are 

 widely separated from the superior series but adjoin the adambulacrals very closely, 

 as there are no intermediate plates whatever. As a result of the widely reticular 

 skeleton, the papular areas on the rays are large and conspicuous. On the disk they 

 are small or moderate, each with one, or rarely two papulae. On the rays, each 

 papular area is wider (or higher) than long and contains 2-5 papulae; these are usually 

 arranged in a vertical series but are occasionally more scattered. The area may also 

 contain an isolated calcareous plate or may be more or less bisected by a calcareous 

 projection from one of its boundary plates. The areas between the two series of 

 marginal plates are about 2| mm. high by one millimeter long and generally contain 

 three (or two) papulae. 



The adambulacral plates are very numerous, about twenty to an octet of infero- 

 marginals; they are small, the width about equal to the length and about two thirds 

 of the height. Each plate carries one spine, 1.5 mm. long; in addition many plates 

 have, usually on the inner margin, a large forficiform pedicellaria almost a millimeter 

 high. Each inferomarginal plate carries, close to the adambulacral series, a spine 

 2 mm. long; these are the stoutest spines found on the animal. They are distinctly 

 rough under a lens, more so than any of the other spines. Oral plates short; each 

 carries two, or less commonly three, spines a trifle longer than those on the adambula- 

 cral plates; generally two large forficiform pedicellarise are also present. 



Tube-feet large, in two well-marked series. Madreporite small, little more than a 

 millimeter across, close to margin of disk. Color completely lost; the preserved 

 specimen is the usual dingy brownish-yellow, approaching white. 



Type. Cat. No. - , U. S. X. M., from Station 5675. 



Although this species resembles the following in form and size, it is dis- 

 tinguishable at once by the more numerous papulae and the characteristic 

 adambulacral armature. The forficiform pedicellarise are also larger and 

 much more numerous. The large size marks this species, in comparison 

 with other members of the genus, for except the Indian species at rat us 

 Alcock, which doubtless deserves separate generic rank, and the Panamic 

 species improvisus Ludwig, with which it was taken, it is the giant of the 

 genus. None of the Arctic, Atlantic or Antarctic species of the genus are 

 half as large. 



Station 5075. Southwest of San Cristobal Bay, west coast of Lower 

 California, 284 fins. Bottom Temp., 44.6. One specimen. 



Pedicsllaster improvisus. 



Ludwig, 1905. Mem. M. C. Z., Vol. 32, p. 216. 



The specimen representing this species was taken with the one just 

 described, and as it is in very poor condition, it was at first supposed to be 



