58 VERRILL 



gg. Rays thick and high at base, rapidly tapered. Dorsal spines few, stout, 

 blunt, or conical, mostly isolated, but forming imperfect median 

 radial rows and a regular pentagon on the disk. Superomarginal 

 spines one to a plate. Inferomarginal row double. Large dermal 

 pedicellariae numerous, stout, stone-hammer-shaped, with serrate 

 jaws. 

 P. papulosus Ver., p. 91. Puget Sd., Brit. Columbia. 



ff. Rays normally six, rarely five; more slender. Dorsal spines short, rather 

 numerous, obtuse or capitate, irregularly arranged, often in groups 

 of two or three. Interactinal spines in two or three rows. Major 

 pedicellariae acute-triangular. 

 P. grayi Ver. = katherinae Per. (non Gray), p. 97. Oregon. 



CC. Rays five; angular, more slender. Dorsal spines in three or five regular 

 rows. Dorsal ossicles stout in longitudinal and transverse rows. 



h. One or two rows of interactinal plates and spines. Major pedicellariae 

 large, ovate; minor pedicellariae not very abundant. Superomar- 

 ginal spines one to a plate. 

 P. paucispinus (Stimp.), p. 98. Calif, to Puget Sd. 



AA. Dorsal spines in three regular rows, bearing dense subapical clusters of 



minor pedicellariae. Superomarginal spines only on alternate plates. 



Ventral spines in two or three rows. Interactinal plates feebly 



developed. 



Marthasterias sertulifera (Xantus), p. 100. Gulf of Calif, to S. Diego. 



3'. Adambulacral spines two to a plate, arranged in two rows (diplacanthid) ; 

 or else in irregular rows, when some of the plates have one and 

 some two spines (subdiplacanthid). 



B. At least one row of visible interactinal plates generally present in adults, 

 often spineless; sometimes several close rows. - * *& 



F. Dorsolateral plates rather small, narrow, strongly lobed, usually reticulated 



or irregularly arranged, and united by their own lobes and by 

 smaller transverse ossicles. 



G. Interactinal plates usually form one long row (peractinal), much like the 



lower marginals, and one or two short proximal rows (subactinals), 

 but the latter may be mostly lacking or rudimentary, especially in 

 the young, so that there may be only two simple rows of ventral 

 spines ; or the lower marginals and peractinal rows may be doubled 

 proximally, two or more spines standing on each plate; thus the 

 number of actual rows of these spines may sometimes be four or 

 more. Dorsal ossicles variously arranged, most often openly reticu- 

 late. Major pedicellariae usually small, ovate or lanceolate, some- 

 times unguiculate. Rays normally five or six. 



H. Dorsal papular areas usually large; papulae small and numerous, in groups 

 of twelve to fifty or more, in the adult. Size generally rather large. 

 Larva of many, if not all, species is a free-swimming brachiolaria. 

 Genital pores dorsal. 

 Genus Asterias (L.), closely restricted, p. 101. 



i. Rays normally five, ossicles and spines reticulate in arrangement. 



