ASTEROIDEA 73 



Development unknown, but the large, yolky eggs indicate 

 that it has probably direct development, without a pelagic larval 

 stage. It appears to reach full size in the course of four years. 

 It prefers a muddy bottom. It would appear that ciliary currents 

 play an important role in its feeding, and that its food consists 

 of minute organisms and detritus. 



In British seas this species is common in depths of ca. 400- 

 800 m. from off S.W. Ireland to the Faroe Channel ; along the 

 Xorth Sea coasts it does not occur. Elsewhere it is distributed 

 from Spitzbergen and the Siberian Sea to the Bay of Bisca}^ and 

 from the Davis Strait to 42° N. on the American side of the 

 Atlantic. Its bathy metrical distribution is ca. 20-1960 m. 



This is a very polymorphic species and has given rise to the 

 establishment of various species which cannot be maintained, or, 

 at most, must rank as varieties. The following varieties may be 

 distinguished : 



Var. platynota Sladen. The alternation of the marginal plates 

 rather indistinct ; papularium inconspicuous ; paxillae generally 

 with a conspicuous central spine ; pedicellariae on adambulacral 

 plates well developed. Colour intensely red, 



Var. nitida Koehler. Arms narrow from the base, not passing 

 so very gradually into the disk. Upper marginal plates not seen 

 on the dorsal side in the interradii : their spines smaller. The 

 central sj^ine of the paxillae small. The proximal adambulacral 

 spines each with a pedicellaria. 



Var. Marionis Perrier. No distinct central spine of paxillae, 

 or a very inconspicuous one. Xo pedicellariae. Spines on 

 marginal plates rather small. Colour lighter. 



The two former varieties are mainly cold-water forms, the 

 third a warm- water form. But this is not quite without excep- 

 tion, and none of the characters are quite constant. 



2. Benthopecten Verrill. 

 (Sj^. Pararchaster Sladen.) 



Disk small, arms long, tapering ; dorsal side with single spines 

 or groups, no paxillae. Marginal plates with prominent spines. 

 A large, odd interradial marginal jilate, the upper one generally 

 bearing a very conspicuous spine. Adambulacral plates with a 

 comb of small, uniform furrow spines, and one or more larger 

 spines on the outer side. Pedicellariae pectinate. 



One species known from the British seas, but one or two 

 more may be expected to occur there also, viz. BentJiopecten 



