86 ECHINODERMS OF THE BRITISH ISLES 



Subfamily PSEUDARCHASTERINiE 



4. Pseudarchaster Sladen. 



Arms rather long, mostly ca. 3 times the disk radius. Dorsal 

 side covered with paxillse ; they continue to the end of the arms, 

 none of the upper marginal plates joining in the dorsal mid-line. 

 Marginal plates wholly covered with grains, the lower marginals 

 mostly also with some larger, appressed spines. Oral interradial 

 area fairly large, covered with grains and spines, more rarely 

 with grains alone. The grains along the sutures of the plates, 

 especially those adjoining the adambulacral plates, often regularly 

 arranged so as to form with those of the adjoining plate a sort of 

 pedicellarise (pectinate pedicellarise, see Fig. 26, 2); small bivalve 

 pedicellariai may also occur. 



Only one species, Ps. Parelii, known from the British seas, 

 but very probably more species will be found to occur there. No 

 less than nine other species have been recorded from the area 

 Bay of Biscay, Azores, Cape Verde Islands, viz. Pseudarchaster 

 (Astrogonium) fallax (Perrier) (known from off the Azores and 

 off the N. American coast, ca. 1100-2200 m.) ; Ps. {Astrog.) 

 necator (Perrier) (Azores, ca. 1250-1900 m.) ; Ps. {Astrog.) 

 annectens (Perrier) (Bay of Biscay, Azores, ca. 900-1900 m.) ; 

 Ps. {Astrog.) hystrix (Perrier) (off Morocco, 840 m.) ; Ps. (Astrog.) 

 aphrodite (PeTTiev) (off Morocco, 1090 m.) ; Ps. {Astrog.) ceguabile 

 (Koehler) (Azores, 1900 m.) ; Ps. {Astrog.) eminens (Koehler) 

 (Azores, 1095-1940 m.) ; Ps. {Astrog.) marginatus (Koehler) (off 

 the Azores, 1805 m.); Ps. {Aphroditaster) gracilis (Sladen) (off 

 the Azores, 1800 m.). The author not having had an oppor- 

 tunity of studying all these species on authentic specimens, and the 

 descriptions and figures found in the literature being more or less 

 unsatisfactory, a key cannot be given, and reference can only be 

 made to the three works containing the descriptions, viz. Perrier 's 

 Echinodermes du" Travailleur" etdu" Talisman'' (1894), Koehler's 

 Echinodermes, Res. Camp. Scientif., Monaco, fasc. xxxiv. (1909), 

 and Sladen's " Challenger " Asteroidea. But it may well be 

 suggested that most of these nine " species " will ultimately 

 prove to be untenable and to be synonyms only of some other 

 species. 



