ASTEROIDEA 79 



British seas ; but it seems unnecessary to enter here on the 

 characters of these subfamilies. 



The Goniasteridse is one of the most difficult groups of the 

 Asteroids, especially because of the very intricate synonymy, due 

 to the insufficient definition of the older genera ; the various 

 species may be found under almost any of the older generic 

 names in literature. Too great splitting up of the species has 

 also added to the confusion. 



Five genera are represented in the British seas, but three more 

 may be expected to occur there also and are therefore in- 

 cluded in the key to the genera. These are : Peltaster Verrill 

 (one species, Peltaster nidarosiensis (Storm) (s}ti. Goniaster 

 jiidarosiensis Storm, Goniaster acutus Llitken, Peltaster hebes 

 Verrill), known from the Norwegian coast, S. of Iceland, and 

 from the West Indies ; 470-ca. 950 m. ; a very large pentagonal 

 form, reaching a size of 25 cm. diameter) ; Paragonaster Sladen 

 {Paragonaster suhtilis Perrier, known from the Bay of Biscay, 

 4700 m., and the Azores, ca. 3000 m). To this species are referred 

 as synonyms : Paragonaster strictus Perrier, P. elongatus Perrier, 

 P. cylindratns Sladen, and P. formosus Sladen, which gives a 

 distribution from the Bay of Biscay to 1° 47' N. on the European 

 side of the Atlantic and from 41° 7' N. to 24° 33' N. on the 

 American side, and a bathymetrical range of 2455-4700 m. ; 

 SpJiceriodiscus Fisher {Sph. {Stephanaster) Bourgeti Perrier, known 

 from the Azores and off the Cape Verde Islands, 410-760 m.). 



Key to the genera of Goniasteridce known from or likely to occur 

 in the British seas. 



1. ]Marginal j^lates with a strong spine . . 5. Hippasteria Gray 

 Marginal plates with only fine grains . .... 2 



2. Upper marginal plates join in the mid-line throughout nearly the 



whole length of the arms, which are long and slender 



3. Nyrnphaster Sladen 

 At most the 2-3 outer upper marginals contiguous . . 3 



3. Arms of medium length, R =ca. 3 r . . . . .4 

 Arms short, body rather pentagonal, K=ca. r3-2 r . .5 



4. Arms very narrow. Upper marginal plates separated by a single 



series of dorsal plates, which have not the shape of paxillse ; 

 no pedicellarise ..... Paragonaster Sladen 

 Arms rather broad. Upper marginal plates separated by several 

 series of dorsal plates ; pectinate or valvate pedieellariaj 



4. Pseudar chaster Sladen 



5. Second or third marginal plate from the point, in both series, 



enlarged ...... Sphceriodiscus Fisher 



Marginal plates evenly decreasing towards the end of arm . 6 



