184 NATURAL HISTORY BULLETIN 



rier. The description of the latter is not sufficiently precise, 

 and in respect to the adambulacral spines, it is somewhat am- 

 biguous. The description, so far as it goes, would indicate that 

 it is a distinct species, but a reexamination of the type is neces- 

 sary in order to determine this with certainty. 



ASTROPECTEN AMERICANUS VcrriU. 



Archaster americanus Verrill, Amer. Journ. Sci., vol. xx, p. 402, 1880; Expl. 



by Albatross in 1883, p. 542, 1885. 

 Astropecten amerivarms VeiTill, Proc. Nat. Mus., vol. xvii, p. 255, 1894; 



Distribution New Eng. Echinod., p. 133, 1895. 



Plate xvi; figures 1-la 



The body is decidedly flat and thinner than in most species. 

 Rays long, slender, tapering to rather acute tips. 



The type had the radii 12°^'° and Ti'^'" ; ratio, 1 :6.16. It be- 

 comes considerably larger than this, with the larger radius up 

 to 85""™ or more. Ratios vary from 1 :5.25 to 1 :6.25. The radius 

 of the disk is equal to the length of the first eight marginal plates. 



Among several thousands, a few were found with six and some 

 with four regular rays. 



The dorsal paxillary area is rather wide; at the base of the 

 rays it is about four times as wide as the opposite plate. The 

 paxillae are small, with a slender elevated column, and a diver- 

 gent group of six to ten or more very slender elongated 

 spinules, sun^ounding one or two central ones of similar size and 

 form. They form narrow transverse rows on the rays. The 

 rows are openly spaced so that the rather large and numerous 

 papular pores can usually be seen. There is a narrow median 

 band destitute of papulae, where the paxillas do not stand in rows. 



The superomarginal plates are relatively small and numerous 

 (40 to 50 or more), becoming very small toward the acute tips 

 of the rays. At the base of the rays their width is about one- 

 fourth that of the paxillar area. They are rectangular prox- 

 imally, broader than long, with nearly straight, deep and wide, 

 transverse, densely fasciolated grooves; distally they become 

 nearly square, with slightly oblique sutures. Proximally the 

 outer and upper surface is usually transversely flat or distinctly 

 concave, owing to the presence of a thickened margin next the 



