NEW STARFISHES FROM THE PACIFIC COAST 137 



in the entire absence of rudimentary annular or calcareous 

 ridges at base of ray, in the abortion of alternate superomar- 

 ginal plates beyond base of ray, and in the small widely spaced 

 inferomarginals each bearing a slender spine ; in the greater 

 prominence of the adambulacral plates which are placed on the 

 same level with the inferomarginals (and each with a single 

 spine as in Pycnopodia) ; in the less crowded condition of the 

 ambulacral ossicles. 



The circular isolated plates on abactinal surface of rays are 

 more numerous than in Pycnopodia and each bears a wreathed 

 spine, whereas in Pycnopodia spines are rare on abactinal plates 

 of arm. There are no large bivalved pedicellariae as in Pyc- 

 nopodia. Tube-feet quadriserial except at extremity and base 

 of ray where they are biserial. Ambulacral plates being less 

 crowded, the tube feet are really intermediate in arrangement 

 between the biserial and quadriserial type. Mouth plates are 

 more prominent than in Pycnopodia and approach in form 

 the type common to Brisingidae. Actinostome wide, like the 

 Brisingidae. 



Named for Dr. Richard Rathbun. 



RATHBUNASTER CALIFORNICUS Fisher, new species. 



Rays 17 (varying from 13 to 17). R = 155 mm. (variable); 

 r = 23 mm. R = 6.Jr (variable). Breadth of ray at base, 9 

 to 11 mm. 



Disk nearly flat, circular; rays long, slender, Brisinga-like, 

 deciduous, more or less constricted at base, adjacent to disk. 

 Abactinal integument thin, transluscent on rays, thicker on disk ; 

 abactinal skeleton reduced to small circular plates, widely 

 spaced, each bearing a slenderneedle-like spine heavily wreathed 

 with pedicellariae; a single superomarginal spine to each plate, 

 widely spaced ; a single inferomarginal spine to each plate, twice 

 as numerous as superomarginals ; a single long slender adambu- 

 lacral spine to each plate. Numerous long vermiform papulae. 



Disk resembling that of a Brisinga in general form, only 

 larger, the rays being very insecurely connected and therefore 

 readily broken off. Rays in general form suggesting those of 



Proc. Wash. Acad. Sci., August, 1906. 



