354 BULLETIN le, UNITED STATES NATIONAL MUSEUM. 



Remarl-s. — Pte.raster marsippus differs from jordani in a number of details 

 mentioned in the diagnosis. The calcareous microscopic rods in the supradorsal 

 membrane are not found in jordani. In young jordani the spiracula are readily 

 seen, while in marsippus they can not be detected. Neither have I been able 

 surely to make them out in the adult. The additional mouth and adambulacral 

 spine seems to be a constant difference, and especially the little side pocket just 

 back of the aperture papilla, between any two fans of spines. This disappears in 

 dried specimens. Unique examples of Pteraster should never be dried, as many 

 valuable characters of the membranes are obUterated, never to be restored. A 

 dried Pteraster is comparable to a dried fish ; neither is a satisfactory verisimilitude 

 of the live object. 



From Pteraster militaris, which dwells in the same region and is similar in 

 proportions, the present species differs in having four-ranked tube feet (except 

 young), in lacking the crowded deposits in the supradorsal membrane, and in 

 having fewer adambulacral and mouth spines. The actinal mouth spine is slen- 

 derer than in militaris, which also does not possess the little pockets between the 

 outer ends of the adambulacral combs. 



PTERASTER COSCINOPEPLUS Fisher. 



PL 102, figs. ], 3; pi. 116, fig. 4. 



Pteraster coscinope plus Fisher, Ann. and Mag. Nat. Hist., ser. 8, vol. 5, Feb., 1910, p. 169. 



Diagnosis. — St«llato-pentagonal. R = 30 mm.; r = 21 mm.; R = 1.4 + r. 

 Breadth of ray, omitting lateral fringe, 22 mm. ; with lateral fringe, 25 mm. Supra- 

 dorsal membrane without special muscle bands connecting summits of spines, but 

 vsath a fine reticulation; spiracula very numerous, small; no spicules; paxillse with 

 high pedicels and six to eight spines; actinolateral membrane very wide, the fi'ee 

 border defining entire ambitus; six webbed adambulacral spinelets; one very slen- 

 der suboral spine; six slender free marginal mouth spines. 



Description. — Abactinal surface covered with protuberances, the ends of the 

 paxillar spines. Membrane moderately thick, slightly translucent, without coarse 

 muscular reticulations, and without calcareous deposits, but with a fine reticulum 

 of muscle fibers, the tiny not well-defined meshes of which inclose the small spi- 

 racula, one to a mesh. The fine fibers radiate from the summits of the spines, 

 crisscrossing in every direction. Spiracula very numerous and small, occurring in 

 short rows between the spines, or radiating from the central spine of a group or in 

 a circle about a spine; much more numerous than in frigonodon. Pedicels of 

 pseudopaxillse relatively high (3 mm.), of about the same proportions as in trigono- 

 don, and much higher than in militaris, jordani, and marsippus. Spines six to 

 eight to each pseudopaxilla, subecjual, and about as long as the pedicel. Osculum 

 large, surrounded by many spines. 



Ambulacra of medium width; tube feet biserial, not crowded. Adambulacral 

 spines six, the inner the shortest and set aborally to the rest; the second about 

 t\snce as long, the third slightly longer; the next three subequal; the outermost, or 

 next one, longest. Web slightly emarginated, the spines having a blunt membra- 

 nous tip; web extends a slight distance beyond end of outermost spine on actino- 



