ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER. 123 



conical, on tho actinal surface. Well-developed dorsal muscle bands, attached to 

 one or two proximal ambulacral ossicles and adjacent superomarginals. 



RemarJcs. — The genera Gheiraster, Pontaster, and Peclinaster are very closely 

 related and have been combined in the past under tho generic title of Gheiraster 

 (Ludwig, 1905; Fisher, 1906, 1910). Ludwig (1910) has lately used the papularia, 

 jjedicollaria, and subunibulacral spines as primary characters for distinguishing 

 the groups. I find also a very useful feature in the mode of attacliment of the 

 proximal end of tho two dorsal muscle bands. 



In Pontaster ami Pectinaster the papularia are entire and swollen, wliile in 

 CJieiraster and Luidlaster they are flat and two-lobcd. Pontaster is distinguished 

 from Pectinaster, in wliich the pedicellaria? arc fasciculate and on any plates but 

 the adambulacrals, by having two-jawed pedicellariaj on the adambulacrals onl}'. 

 Luidiaster and Pectinaster differ from Gheiraster in having the dorsal muscle bands 

 attached to one or two of the proximal ambulacral ossicles (near where they abut 

 against the superomarginals) as well as to the adjacent superomarginals; Gheiraster 

 has the muscles attached to the superomarginals and abactinal plates, but not to 

 the ambulacrals. Glieiraster has only one subambulacral spine, Luidiaster has 

 two or more. 



Tlie following species is a typical Pectinaster, with highly specialized papu- 

 larium and the maximum distribution of pedicellaria\ 



PECTINASTER AGASSIZI EVOPLUS (Fisher). 

 PI. 28, figs. 1, 2; pi. 55, figa. 4, 4a; pi. 57, fig. 1. 

 Cheiraster agassizi evoplus Fisher, Zool. Anz., vol. 35, March 29, 1910, p. 551. 



Diagnosis. — Differing from Pectinaster agassizi (Ludwig) in having abactinal 

 and intermarginal pedicellaria^ antl usually larger papular areas with more numerous 

 papular pores. Rays five; R = 72 mm.; r=ll.,5 mm.; R = 6.4 + r. Nearly related 

 to Pectinaster jUholi (Perrier) and Pectinaster mimicus (Sladen). Rays long, 

 slender, evenly tapered from the base to an attenuate extremit\'. General form 

 very much as in P. mimicus, but rays shorter and slightly slenderer. Abactinal 

 surface ^vith numerous small, roundish, low, spaced paxillse; larger ones with a 

 delicate central spinule and a crown of eight to fifteen small spineiets, interspersed 

 with more numerous smaller ones lacking the spinule, the former extending abund- 

 antly to tip of ray; a variable immber of small pectinate or, more rarely, fascicular 

 pedicellarife on the abactinal surface. Papuhe confined to an oval papularium at 

 base of ray, forty to seventj'-fivo pores to each area in adult specimens. Acces- 

 sory supermarginal spinules on first five or si.x plates, one to three (rarely four) 

 accessory inferomarginal spinules on proximal third or half of ray, only one beyond, 

 and merely the single primary spine on distal fourth of ray; adambulacral plates 

 with five to nine furrow spineiets, and one actinal with a small companion; actinal 

 intermediate plates extending as far as the sixth to tenth inferomarginal. Pedi- 

 cellariae numerous on interradial areas, and present on suture between marginal 

 plates, on inferomarginals, and also sometimes betwieen inferomarginals ami inter- 

 mediate plates, and between inferomarginals and adambulacrals. 



Description. — Larger paxilla; of abactinal surface slightly elevated, the summit 

 bearing an acicular, slender, very delicate spinuLe about 0.75 to 1.5 nun. long, sur- 



