80 ECHINODERMS OF THE BRITISH ISLES 



6. Covering of dorsal side arranged in the form of paxillgc 



1. Ceramaster Verrill 

 Covering of dorsal side not in the form of paxillai . . 7 



7. Dorsal plates closely granulated ; large bivalve pedicellarise, both 



on upper and under side .... Peltaster Verrill 



Dorsal plates naked centrally, surrounded by a single series of 

 granules on the radial areas ; pedicellarise small 



2. Plinthaster Verrill 



Subfamily Goniastertn/E 

 1. Ceramaster Verrill. 



Body mostly pentagonal ; arms short, sometimes so short as 

 to represent merely the corners of the body. 1-3 of the distal 

 upper marginals joining in the dorsal mid-line. Dorsal plates 

 entirely covered with granules, arranged in sharply limited 

 groups, resembling paxillse. Marginal plates covered with 

 granules, but often with a naked part in the middle. Oral inter- 

 radial plates covered with granules. Pedicellariae small, bivalved, 

 or with two or three spatula te jaws, usually not in deep pits. 



Three species are recorded from the British seas, but one more 

 is likely to occur there also, viz. Ceramaster placenta (Miill. and 

 Troschel) ; (syn. Goniodiscus placenta Miill. and Troschel ; 

 G. placentceformis Heller ; G. acutus Heller ; Pentagonaster 

 mirabilis Perrier ; (?) P. crassus Perrier ; Pentagonaster minor 

 Koehler), known from the Bay of Biscay (ca. 200-400 m.), and 

 from the Mediterranean (10-160 m.). Also Ceramaster (Penta- 

 gonaster) Vincenti Perrier, from off Morocco, 946-1105 m. 

 (" Talisman ") may possibly occur in the British seas. These 

 species, therefore, are included in the key. 



One of the species recorded from the British seas (S.W. of 

 Ireland, 1800 m., " Flying Fox '*), Ceramaster Greeni (Bell) is too 

 insufficiently known to be placed in the key, and, for the present, 

 reference can only be given to the description and figure given in 

 Bell's Catalogue, p. 74. ^ 



^ Dr. C. C. A. Monro has kindly given me the following additional informa- 

 tion about the type-specimen which is in the British Museum. The mar- 

 ginal plates are — or were once — covered with a fine granulation, but whether 

 they were wholly or only partly covered is impossible to say, because all 

 the grains have been rubbed off, except in a few patches. The marginal 

 plates appear to be all alike, and Bell's figure gives a good idea of their 

 general outline. The madreporite can only be distinguished with difficulty. 

 Bell's figure being wliolly misleading in this particular. The paxillae of 

 the dorsal side are round, witli ca. 12-16 peripheral and ca. 7-15 central 

 granule-like spinelets. 



