SHALLOW-WATER STARFISHES 325 



The terminal or ocular plate of the rays is relatively large, thick, 

 trapezoidal, longer than wide. It is reached by about two or three 

 rows of very small dorsal plates. 



No pedicellariae were found. 



Off San Francisco (Prof. W. E. Ritter). Only one specimen seen. 



Genus Leptychaster Smith. 



Leptychaster SMITH, Ann. and Mag. Nat. Hist, ser. 4, xvn, p. no, 1876. 

 Leptoptychaster SMITH, Phil. Trans. Roy. Soc., Zool., CLXVIII, p. 278, 1879. 

 / Parastropecten LUDWIG, Mem. Mus. Comp. Zool., xxxn, p. 76, 1905. 

 Leptychaster (pars) FISHER, op. cit., 191 ib, p. 42. 



Stellate, with five short rays, rarely six ; disk broad. 



Marginal plates, thick, oblique, at least distally, the upper ones 

 often smaller than the lower and not encroaching much on the abac- 

 tinal side, proximally; prominent or carinate in the middle, with 

 wide and deep fasciolated grooves between them ; covered with small 

 spinules, which become larger in the grooves. Dorsal plates are true 

 paxillse, with roundish or somewhat stellate bases, in the papular 

 areas ; their spinelets are usually very small and numerous. 



The interactinal plates form an important triangular area. They 

 are spinulose, thick or carinate, with deep fasciolated grooves 

 between them. They are arranged in transverse rows running to the 

 adambulacral plates ; or they may be said to be in rows parallel with 

 the ambulacra, with a few unpaired interradial plates. The trans- 

 verse rows of interactinals nearly correspond in number to the mar- 

 ginals, except in the middle of the interradial areas, where there are 

 more. The adambulacral plates have a group of slender furrow- 

 spines and a divergent group of similar ones on the actinal side. 



Dr. Fisher thinks that Parastropecten Ludwig and Glyphaster 

 Verrill should be united with Leptychaster. 



The discovery of L. pacificus and other somewhat intermediate 

 forms renders this view somewhat reasonable. It would seem, how- 

 ever, that Glyphaster can be retained at least as a subgenus, if not a 

 genus, for those species which, like anomalus, have robust and 

 squarish upper marginal plates, and the abactinal plates of the 

 papular areas only slightly lobed. The inferomarginal plates are 

 not oblique in the latter, and each corresponds to two rows of inter- 

 actinals instead of one. 



Whether Parastropecten Lud. is strictly synonymous with Glyph- 

 aster is uncertain. The type is P. inermis Lud. 



The type of Leptychaster is L. kerguelenensis Smith, from the 

 Antarctic. In a later paper he used a revised spelling of the word 



