74 ECHINODERMS OF THE BKITLSH IHLKH 



{Parar chaster) Fischeri (Perrier), known from off the N.W. coast 

 of Africa (25° 39' N., 18° 26' W., 1056-1435 m., " Talisman "), 

 and S. of Iceland (62° 10' N., 19° 36' W., 2060 m., " Thor "),i 

 and B. {Parar chaster) Folini Perrier, known from off the Cape 

 Verde Islands (ca. 2320 m.). It may therefore be preferable to 

 give a key to distinguish these species, while otherwise only the 

 species actually known from British seas, B. armatus Sladen, is 

 described in more detail. 



Key to the species of Benthopecten known from or likely to occur 

 in the British seas. 



1. Upper odd interradial marginal plate with a single (rarely two) 



very prominent spine ....... 2 



Upper odd interradial marginal plate with several not very 

 prominent spines ; pectinate pedicellariae between the lower 

 marginal plates ...... B, Folini 



2. No pedicellariae between the lower marginal plates 



1. B. armatus 

 Pectinate pedicellariae between the low^er marginal plates 



B. Fischeri 



1. Benthoj)ecten armatus (Sladen). (Fig. 41.) 



(Syn. Pararchaster armatus Sladen ; Pararch. semisquamatus 

 var. occidentalis Sladen.) 



Dorsal side with small spines, 1-3 on a plate, not forming 

 paxillse. Marginal plates each with a single large spine and gener- 

 ally a few small spinelets, but sometimes wholly naked, excepting 

 the large sj^ine. The lower marginals, especially in larger 

 specimens," usually with a second, somewhat smaller, spine below 

 the first, larger one. Adambulacral spines with a comb of 5-7 

 small cylindrical furrow spines and 'one large spine, and one or a 

 few small spinelets on the outer side. Pectinate pedicellariae may 

 occur on the dorsal side and on the oral interradial areas, but 

 apparently not between the lower marginal plates. R = ca. 6 r. 

 Largest size recorded, 6 cm. R. 



Colour in life, biology, development unknown. 



In the British seas this species has been found at 51° 22' N., 



^ The latter may perhaps rather represent a separate species, but is, 

 in any case, nearest related to B. Fischeri. The latter has recently (Grieg, 

 1921) been maintained to be identical with B. spinosus Verrill, which is 

 again maintained to be identical with B. armatus Sladen. In the opinion 

 of the present author this is unwarranted, the material at present available 

 not having yielded the intermediate forms to prove tlie identity of the said 

 species. 



