66 VERRILL 



O. leptolena Ver., nov., p. 182. British Columbia. 

 "'WC. No visible interactinal plates or spines. (See below, p. 66.) 

 Genus Distolasterias Per., in part, p. 185. 



Dorsal spines numerous, in about seven to nine irregular alter- 

 nating rows; rather short, fluted, blunt or clavate. Larger major 

 pedicellariae partly stout, wedge-shaped; partly elongated, spatulate, 

 unguiculate, with few large curved teeth. Adambulacral spines 

 slender, crowded, regularly diplacanthid. 



_., D. chelifera Ver., nov., p. 185. Vancouver I. 



JJ. Dorso-lateral plates mostly wide, lobed, overlapping or imbricated in few 

 close rows (stichasterial arrangement), covered with clusters of 

 minute spinules. A distinct peractinal row of plates. Disk small, 

 rays slender, six in type. Ambulacral pores unusually large, sub- 

 triangular or cordate, not crowded. Dorsal spines very small, 

 short, scattered, obtuse or clavate, a distinct median radial series. 

 Stenasterias tnacropora Ver., p. 145. Alaska. 



BB. Interactinal plates lacking or rudimentary ; no interactinal spines. 

 M. Dorsal skeleton weak, composed mostly of slender, openly reticulated 

 ossicles, some of which do not unite in a continuous skeleton. Dor- 

 sal spines few, rather large, in few open rows or scattered; upper 

 marginal spines regular and well separated from lower marginals; 

 the latter with large and long spines ; alternate plates without spines. 

 Minor pedicellariae large and very numerous, in sacculated wreaths 

 or clusters. Size large. 



Genus Urasterias Ver., p. 187. Type, U. linckii (M. and T.). Arctic; 

 North Atlantic. 



b. Several open rows of long dorsal spines ; adambulacral plates not crowded ; 



lower marginal spines large and well spaced; minor pedicellariae 

 not remarkably large; bunched in large wreaths on the large, loose, 

 saccular sheaths of the spines. Size large. 



U. linckii (M. and T.), p. 187 (extralimital?). N. Atlantic and Arctic. 

 MM. Dorsal skeleton well developed. 



c. Dorso-lateral plates and ossicles openly reticulated. Rays regularly five, 



rather short, stout, depressed; dorsal spines numerous, small, 

 slender, obtuse, arranged on small, slender, reticulated ossicles; no 

 distinct median row; marginal spines usually two to a plate in both 

 rows, in form like the dorsals, but rather longer; adambulacrals 

 regularly diplacanthid. No interactinals visible. 

 Genus Parasterias nov., p. 187. Type, P. albertensis Ver. Brit. 



Columbia. 



cc. Dorso-lateral spines and plates in more or less obvious longitudinal or 

 transverse rows ; spines either solitary or clustered. 



d. Rays regularly five, large and long; dorsal plates bear large and mostly 



solitary spines and large pedicellariae. 



Genus Distolasterias Per., in part, p. 185. (See above, p. 65.) 



dd. Rays slender, variable in number, due to autotomy; disk small; autoto- 



mous; finally six or five. Median and marginal plates little wider, 



imbricated in longitudinal rows ; dorso-lateral ossicles and plates 



short, irregularly reticulated, but leaving regular rows of papular 



