New Pterasteridse/rom (he North Pacific. 167 



XXIII. — New Pterasterida^/VtfHi the North Pacific. 

 By Walter K. Fisher, Stanford University, California. 



The new species of Pteraster will be rendered more intelli- 

 gible if contrasted with known forms in the following 

 synopsis. The species mentioned are not all that occur in 

 the region of the North Pacific, but include most of the 

 5-rayed forms. These will be fully figured and described in 

 a later publication. 



Pteraster. 



a. Form stellate; R exceeding 1-8 r, usually 

 2 r or more. 

 b. Tube-feet in 2 series ; supradorsal mem- 

 brane with spiny spicules ; oral spines 

 webbed ; superoral spine stout. 

 o. R=2to 2 - 5r; adambulacral comb with 

 more than 5 spines ; oral spines 6 to 8 ; 

 superoral spine cylindrical, not 3-edged ; 

 paxilla stalk low, with 3 to 5 spines . . militaris (Miiller), 

 cc. R-= 1/87 r ; adambulacral comb with 5 

 spines ; oral spines 5 ; superoral very 

 large, 3-edged ; paxilla stalk high, with 



6 spines trigonodon, sp. n. 



bb. Tube-feet crowded, in 4 series, at least 



proximally ; supradorsal membrane either 



without deposits or with a very few 



simple rods ; oral spines partly or wholly 



webbed; superoral spine slender. 



c. R = 2 r; adambulacral comb of 3 or 4 



spines; oral spines 4 ; no small lateral 



pockets back of aperature papillae ; 



no deposits in supradorsal membrane ; 



paxilla spines usually 2, longer ; spira- 



cula present jordctni, Fisher. 



cc. R = 1'8 to 25 r; adambulacral comb 

 of 5 spines proximally ; oral spines 5 ; 

 small shallow pockets just back of 

 aperature papillae ; supradorsal mem- 

 brane with few scattered simple rods ; 

 paxilla spines 3, shorter ; spiracula 



absent marsippuSy sp. n. 



aa. Form more or lesa pentagonal ; R less than 



1-8 r. 



b. Oral spines 6, free ; superoral spine very 



slender; spiracula very numerous; lateral 



fringe defining ambitus ; no spicules in 



supradorsal membrane ; R= 1-4-j-r coscinopeplus, sp. n. 



bb. Oral spines 5 to 7, the entire 10 to 14 united 

 by a continuous membrane; R = 1'3 r ; 

 deposits present or absent ; abactinal 

 surface swollen and more or less warty in 

 fldult. 



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