PTERASTEK. 



93 



1. PTERASTER. 



Pteraster, M. Tr. Syst. Ast. (1842) p. 127 ; Sladen, Chall. Rep. Ast. 

 (1889) p. 469. 



A Pterasterid in which the adambulacral plates carry transverse 

 combs of spines ; the spines are webbed ; the snpradorsal membrane 

 is provided with muscular fibrous bands, which are not arranged in 

 a reticular manner, and usually contains spicules. 



1. Pteraster militaris. 



Asterias militaris, O. F. Midi. Prod. Zool. Dan. (1776) p. 234, 

 no. 2828 ; J. Rathhe, in Zool. Dan. iv. (1806) p. 13, pi. 131. 



Asteriscus militaris, M. Tr. Syst. Ast. (18-12) p. 44. 



Pteraster militaris, iid. t. c. p. 128 ; Diib. fy Ror. Vet.- Ah. Hdlg. 

 1844 (1846) p. 246, pi. vii. figs. 11-13 ; Stimps. Inv. Grand Manan, 

 (1853) p. 15 ; Ror. 8f Dan. Faun. litt. Norv. ii. (1856) p. 55, 

 pi. viii. figs. 1-8; Lutk. Vid. Medd. 1857, p. 43; Sars, Norg. 

 Ech. (1861) p. 48, pi. iii. figs. 8, 9, pis. iv., v., vi. figs. 1-13; 

 Dig, $ Hup. Echin. (1862) p. 434 ; Moeb. fy Biitschli, JB. Comm. 

 Rid, ii. & iii. (1875) p. 147 ; Perr. Arch. Zool. exp. v. (1876) p. 301 ; 

 Ror. <§• Dan. Norske Nordhavs Asteroidea, (1884) p. 70 ; Slad. 

 Chall. Rep. Ast. (1889) p. 471. 



R=2 r. 



Body high, stellate, the sides of adjoining rays forming a slightly 

 obtuse angle with one another ; ambulacra moderately wide, bounded 

 bv a transverse comb of four to six spines ; this is on its outer side 

 attached to the membrane which connects the marginal spines with 

 one another. The paxilliform spines which bear the supradorsal 

 membrane end in two or three spinelets. 



R=22'5 ; r = 10-5. Greatest height = 13. Breadth of arm at 

 base 14 millim. 



Distribution. Both sides of Xorth Atlantic, as far south as Grand 

 Manan on the west and coast of Norway on the east. A charac- 

 teristic arctic form, and said to increase in size the further north it 

 is met with. 10-600 fms. 



a. Faeroe Channel, 530 fms. ' Triton ' Exp. 



Var. prolata. 



Pteraster militaris, var. prolata, Sladen, Trans. Roy. Soc. Ed. xxxii. 

 (1884) p. 153, pi. xxvi. fig. 1 ; id. Chall. Rep. Ast. (1889) 

 p. 472. 



Mr. Sladen distinguishes a specimen from the Faeroe Channel 

 (608 fms.) in which, " although it accords in the main with the 

 diagnostic formula of that species [i. e. P. militaris'], the majority of 

 the characters differ more or less in degree." The rays are said to 

 be long and narrow. B = 58 to 60 millim. ; r=18 millim. I have 

 not seen the form, and have no opinion to offer. 



