138 ECHINODERMS OF THE BRITISH ISLES 



738-900 m. (" Helga "), (12. v. 1905 ; not hitherto recorded). 

 The species has been found elsewhere only in the Bay of Biscay 

 and off the Azores, 938-1225 m. (" Talisman "). 



IV. Family Asteriid^e 



Rays usually 5 or 6, of medium length, tapering, generally not 

 sharply defined against the disk. Dorsal skeleton of arms mostly 

 irregular, reticulate ; spines single, forming more or less distinct 

 longitudinal series. Generally both crossed and straight pedi- 

 cellariae. Tube-feet in four series. 



Three genera of this family are represented in the British seas, 

 but one more may well be expected to occur there also, viz. 

 Sderasterias Perrier, with the species Sderast. Guernei Perrier, 

 known from the Bay of Biscay, 240-300 m. The species Sderast. 

 neglecta Perrier (Syn. Stolasterias, Stylasterias negleda ; Asterias 

 Edmundi Ludwig), recorded also from the Bay of Biscay, and 

 from the Mediterranean, is scarcely to be distinguished from 

 Sderast. Guernei). Further, there is perhaps a possibility that 

 the genus Coscinasterias Verrill also may be represented on the 

 southern coasts by the species Coscinast. tenuispinus (Lamarck) ; 

 it occurs from the S.W. coast of France to Cape Verde, the Azores, 

 and the Mediterranean, and also at the Bermudas Islands, in the 

 littoral region, down to 40 m. The two said genera, therefore, are 

 included in the key. 



Key to the genera of the family Asteriidoe known from or likely 

 to occur in the British seas. 



1. Adambulacral spines alternating, one and two ; carrying pedi- 



cellariae ......... 2 



Adambulacral spines in a regular single or double series ; not 



carrying pedicellarise ....... 3 



2. Papular areas large, each with numerous small papulae 



1. Asterias Linnaeus 

 Papular areas small, each with few, larger papulae 



2. Leptasterias Verrill 



3. Adambulacral spines in a regular double series (" diplacanthid ") ; 



mid-dorsal and marginal plates forming regular series, each 

 with a single, fairly large spine, surrounded by a wreath of pedi- 

 cellariae ...... Sderasterias Perrier 



Adambulacral spines in a regular single series ( " monacanthid " ) 4 



4. Rays 6 or more ; one series of spiniferous ventre -lateral plates. 



Generally with 2 (3) madreporites. Propagates normally 

 by self -division ..... Coscinasterias Verrill 

 Rays 5 ; one series of ventro -lateral plates, hidden by skin, not 

 spiniferous ; no propagation by self -division. Only 1 madre- 

 porite . . . . . .3. Marthasterias Jullien 



