ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISH Kit. 363 



Cilia in circumscribed areas, as tliey should be in Ritaster. Ii is this circumstance 

 whicli lias led me to keep both forms in Pttra.iter, although for several ^-ears I con- 

 sidered tesselatus a Retaster. 



PTKRASTER TESSELATDS ARCUATUS. new •ubfpecle*. 

 PI. 103, fig. 1. 



Diagnosis. — Similar to Pt. tesselatm, but arcuntely pentagonal in form, with 

 thick supradorsal membrane, without signs of reticulation; spiracula sunken in 

 irregular creases. R=46mm.; r = 32 mm.; R = 1.44r. 



Description. — Supradorsal membrane rather thicker than in typical Usselat'us 

 and marked by fine, irregular, discontmuous, often branching, dark creases, into 

 wliich open the spiracula. These are more prominent on the dorsal than lateral 

 surfaces. Pa.xillar spines eighteen to twenty-four. Adambulacral spines five or 

 six, of which three are usually long and subequal and the two inner decidedly 

 shorter. Of the latter the innermost is about one-third and the second spine two- 

 thirds the length of the third spine. Mouth plates wth si.x marginal spines similar 

 to those of typical tesselaius; suboral spine about as long as innermost marginal 

 spine, and \\'ith a transparent, tapering, sliarp tip. 



Color in life, abactinal surface mottled with fawn color on a ground of bluish- 

 gray or dull iieliotrope purple; radiating from center are five narrow, dark, inter- 

 radial ]>atclies extending halfway to margin, and five radial larger and ligliter areas; 

 outside of this is a stellate, irregular ring of dark, near ambitus. Actinal surface, 

 actinolateral membrane vinaceous buff; interradial areas dull heliotrope purple 

 (that is, outside of the narrow membrane); tube feet, yellowish. 



Type.— C&t. No. 27794, U.S.N.M. 



Type-locality. — Albatross station 4551, Monterey Bay, California, 56 to 46 

 fathoms, rocks. 



Distribution. — Known only from the type, taken in Monterey Bay. 



Remarks. — This form differs from northern tessilatus chielly in the arcuately 

 pentagonal form, generally one less furrow spine, and in having the spiracula in 

 fine, dark furrows, wliich form disconnected, nicandcriiig. branched designs. The 

 reticulations of the supradorsal membrane of tesselatu.i are not evident in arcuatus. 



PTERASTER OBSCURUS (Periitr). 

 PI. 105, figs. 1-4; pi. 106, figs. 1. 2. 



Hexasler obicurus Perrier, ComptOB rendug, vol. 112, Xo. 21, May 1, 1891, p. 1227; M^m.sor. booI. 



Franco, vol. 4, 1891] p. 267; R<''sult. camp. sci. «lu Prince do Monaco, fasc. 11, 1896, p. <1. 



pi. 3, figs. 1, In. — Verrill, Trana. Conn. Acad., vol. 10, 1899, p. 221. — Lvdwio, Arktische 



Seeslerne, 1900, p. 4G8 (dL-<tril)Utiou). 

 PUratter (Tcmnasler) hexactit Verrill, Proc. U. S. Nat. Mus., vol. 17, 1894, p. 276. 

 Pteranlrr hexaclis Doderlein, Zool. Anr.., vol. 22, 1889, p. 338. 

 Temnaaler hcinclis Verrii.i., .Anicr. Jouni. Sci., vol. 49, 1895, p. 202. 

 Pteraslcr ohscurus Doderlein, Wi.sM. Meercsuntereuch., (N. S.) vol. 4, Abth. Ilolgoland, Heft 2, 



1900, p. 213, pi. 8.— MoRTE.ssEN, Meddelelwr om Gr\«nland, vol. 29, 1903, p. 77. 

 Pteraslcr oclasler Verrill, Amer. Joura. Sci., vol. 28, July, 1909, p. 61, fig. 1. 



Diagnosis. — Kays six, seven, eight, or nine form"; robust, rays short, broad, 

 and usually rigid; disk high; R — 1.4 to 1.65 r. Supradorsal membrane tough and 



o Only one pxample, the young of an eight-rayed speciinon. 



