SHALLOW-WATER STARFISHES 67 



areas. All the plates are covered with close clusters of small, nearly 

 equal spinules, longer beneath. Pedicellariae of two sorts ; dermal, 

 not abundant ; few on spines. 

 Stephavasterias albida (St.), p. 147. Circumpolar; North Atlantic; 

 Bering Sea. 

 2' The inner adambulacral spine, on alternate plates, is attached to a lobe of 

 the inner edge of the plate, higher up within the groove. Dorsal 

 spines small and numerous, scattered. Interactinal plates feebly 

 developed or lacking. 

 Allasterias Ver., p. 188. Type. A. rathbuni Ver. Bering Sea. 



f. Dorsal ossicles small, forming reticulations; adambulacral spines alternately 



two and three to a plate. Superomarginal spines clustered. Dermal 

 major pedicellarise large and numerous, pointed. Rays five, wide, 

 depressed ; margin prominent. 

 A. rathbuni Ver., p. 189. Bering Sea. See also, A. fordculosa V., 

 nov., p. 194. Japan. 



g. Inferomarginals not very stout, flattened, blunt, not deeply channeled. 



Subspecies nortonensis Ver., p. 191. Bering Sea. 

 gg. Inferomarginal and actinal spines stout, channeled or gouge-shaped. 



A. anomala Ver., p. 193. Siberia, 

 r. Dorsal skeleton incomplete or rudimentary; ossicles partly isolated; dorsal 

 surface covered by soft skin. Disk large; rays multiple, variable 

 in number, increasing with age by interpolation in pairs up to twenty 

 to twenty- four in the adult. Adambulacral spines monacanthid. 

 Marginal plates distinct. Dorsal minor pedicellariae in large clus- 

 ters, dermal and epispinal. 



Genus Pycnopodia Stimp., p. 197. Type, P. helianthoides (Br.), p. 198. 

 Calif, to Aleutian Islands. 



ASTERIIN^: DESCRIPTIONS OF GENERA AND SPECIES. 



Genus Pisaster A. Agassiz, ex Miiller and Troschel. 



Pisaster Muller and Troschel, Syst. Ast., p. 20, note, 1842. A. Agassiz, 



North American Starfishes, p. 96, 1877 (type, ochraceus). 

 Cosmasterias (pars) Sladen, Voy. Challenger, xxx, p. 562, 1876. 



Large starfishes with a thick and usually broad disk and either 

 five or six stout tapering rays. Adambulacral spines form a single 

 regular row, one to each plate (monacanthid). Three to six rows 

 of closely united or tesselated, thick actinal and lower marginal 

 plates, bearing several close rows of stout ventral spines. The syn- 

 actinal plates are closely united to the adambulacrals. Oral region 

 usually deeply sunken. Interbrachial septa well developed. 



Special, very large, stout, erect, sessile, forficulate pedicellariae, 

 with interlocking serrations at the ends of the valves (unguiculate), 

 stand on the lateral channels, and often between the actinal and 

 dorsal spines ; larger ones often stand in the interradial areas below. 



Dorsal skeleton variable, but well developed, the ossicles generally 



