104 ECHINOpERMS OF THE BRITISH ISLES 



1. Pteraster militaris (0. Fr. Miiller). (Fig. GO.)* 



Arms fairly long and slender. The paxillae of the dorsal side 

 with only 2-4 slender spines. Supra-dorsal membrane with 

 numerous small calcareous bodies. Web connecting the spines 

 along edge of jaws not continuous across the mid-line. Outer 

 surface of jaws with two strong, outwardly directed spines. Only 

 a very inconspicuous median projection of jaws. Adambulacral 

 spines 5. The fin-like membrane fairly broad, partly visible 

 from the dorsal side. R. = ca. 2-5 r. Reaches a size of 75 mm. R. 

 Colour in life yellowish or yellowish-red. 



Biology unknown, but it appears that ciliary currents 2:)lay 



Fig. 60. — Pteraster militaris. Oral side. Nat. size. 

 (From Danmark's Fauna.) 



some part in conveying detritus to the mouth, besides bringing 

 water into the supra-dorsal cavity for serving the respiration of 

 both the specimen itself and the young contained in the cavity. 



In British seas it has been found only in the Faroe Channel 

 (59° 37' N., 6° 49' W., 954 m., " Triton ''), in the Inner Sound, 

 Ross-shire, 36 m. (" Runa "), and on the Lousy Bank. Elsewhere 

 distributed from the Skagerrack to Spitzbergen and the Siberian 

 Sea, from Greenland to 40° N. on the American coast, and to 

 Vancouver in the Northern Pacific ; it is thus a circumpolar 

 species. Bathymetrical distribution, 10-ca. 1100 m. 



The variety jwolata Sladen has somewhat longer arms, R. > 3 r. ; 

 one of spines of the paxillse much more robust than the others. 

 The segmental apertures larger and the aperture papillae broader 



