ASTEBOIDEA OF NORTH PAClflO AND ADJACENT WATERS FISHEB. 345 



KEY TO THE SPECIES OF PTEKASTER HEBEIN DE8CB1BED.O 



o'. Rays constantly five. 

 6'. Form stellate; R exceeding 1.8 r, usually 2 r or more, 

 c'. Suprailurtial membrane reticulated, very thin and delicate; spiraci'Ia six to ten to an area; 



oral 8piiie8 two gracilU, p. 349. 



c'. Supradorsal membrane not reticulated. 



d'. Tube feet in two series; supradoreal nienibraiie with spiny spicules; oral spinco webbed; 

 suboral stout, 

 c'. 11=2 to 2.5 r; adambulacnil comb with more than five spines; oral spines six to eight; sub- 

 oral spine cylindrical, not throe edged; paxilla stalk low with three to five spines. 



miliUtru, p. 346. 

 e'. R=1.87 r; adambulacral comb with five spines; oral spines five; suboral very large, three- 

 edged; paxilla slalk high with six spines trigonodon, p. 348. 



cP. Tube feet crowded, in four ticrie.-*, at least proximally; supradorsal membrane either without 



deposits or with a very few simple rode; oral spines partly or wholly webbed; suboral 



slender. 



e'. R=2 r; adambulacral comb of three or four spines; oral spines four; no small lateral pockets 



back of aperture papillse; no deposits in supradorsal membrane; paxilla spines usually 



two, longer; epiracula present jordani, p. 350. 



«». R=1.8 to 2.5 r; adambulacral comb of five spines proximally; oral spines five; small shallow 

 pockets just back of aperture papilla?; supradorsal membrane with few scattered simple 



rods; paxilla spines three, shorter; spiracula absent martippxu, p. 352. 



6'. Form more or lees pentagonal, R less than 1 .8 r. 

 c'. Oral spines six, free, suboral spine very slender; spiracula very numerous; lateral fringe defin- 

 ing ambitus; no spicules in supradorsal membrane; R = 1.4 r coscinopeplui, p. 354. 



c'. Oral spines five to seven, the entire ten to fourteen united by a continuous membrane, 

 d'. Size large; membranes thick; supradorsal membrane more or less reticulated by muscle bands, 

 or else creased by fine furrows into which open the spiracula; actinolateral membrane very 

 narrow. R=1.44 to 1.8 r. 

 e'. With well developed rays; reticulations usually evident at least on sides of body. R=1.6 



to 1.8 r Ussflalut, p. 359. 



e'. More arcuately pentagonal in form. R=1.44 r; no evident reticulations; supradorsal mem- 

 brane with many fine irregular disconnected creases arcuatiu, p. 363. 



rf". Size medium or small; membrane rather thin, often translucent. R=1.3 r; deposits present 



or absent; abactinal surface swollen and more or less warty in adult. 



e'. Paxilla; with high pedicel and five to fifteen (five to seven in AUiskan specimens) spines; 



suboral spine slender cylindrical; muscle bands connecting tips of paxillar spinelcts; 



aperture slits small; oral spines six or seven; no depoeitd in supradorsal membrane; 



lateral fringe not defining ambitus pulvillut, p. 358. 



«*. Paxilla; low, with low pedicel and five to seven short spines; suboral spine with three sharp 

 edges; no muscle bands connecting lips of paxillar spinelet."; aperture ."lils unusually 

 large; oral spines five; in supradorsal membrane dcixwits in the form of branched rods; 



lateral fringe defining ambitus <<7/ino<-^rton, p. 356. 



c*. Oral spines three, each scries independently webbed; abactinal surface not much elevated and 



not at all warty multispinus, p. 359. 



a'. Rays six, seven, or eight, very rarely nine; lateral fringe when e\-ident narrow, defining ambitus; 

 supradorsal membrane, actinolateral membrane, and webs heavy, spiracula numerous; abactinal 

 surface rough and spiny; adambulacral spines four to seven; oral spines five or six, completely 

 webbed. R=1.4 to 1.65 r obieunu, p. 363. 



o I have not included in the key Vcrrill's Plerailer hebrs (1909o, p. 61), as I am not sure that it is a 

 PteratUr. Profea^or W'rrill has sent mo two views showing tlie lateral and abactinal surfaces. The 

 creature greatly ri'semble,^ a Piplopltrastrr. The typo lacked mouth plates, and the presence of mu.«-lo 

 bands and spiracula in the supradorsal membrane is not indicattHl. II it i.H a Diploptamlrr it would 

 seem to bo distinrt from miiltijxi. (Departure Bay, British Columbia, 23 fathoms, mud and sand.) 



