30 ECHINODERMS OF THE LONDON CLAY. 



3. Astropecten ? Colei. Plate IV, fig. 3. 



Among some fragments of fossil star-fishes obtained by the Earl of Enniskillen in the 

 London Clay of Sheppey, and now in the Museum of Practical Geology, is one belonging 

 to a very distinct type from any described, but unfortunately too imperfect to afford 

 certain indications of its generic affinities. I have placed it provisionally under Astropecten. 

 It may, however, be a Luidia. 



It consists of portions of two, if not four rays, evidently originally, as the parallelism 

 of their sides indicates, of very considerable length. Their margins are bordered by two 

 series of narrow plates, each bearing an elevated crest or ridge, with very steep sides. 

 These ridges bear traces of pits for the attachment of spines. Those of the inferior plates 

 are gently curved, and become broader and flatter towards the avenues. Within them, 

 towards the avenues, are broader polygonal plates, with strongly marked spine-sockets. 

 The spines that lie about are stout at their bases, and taper gradually to an obtuse 

 extremity. Complicated arrangements of small spines bordered the avenues. The diameter 

 of one of these arm fragments is eight twelfths, and the thickness five twelfths of an inch. 



Genus — Goniaster, Agassiz. 



The star-fishes of this genus have pentagonal bodies covered by tesselated ossicula, 

 which are usually ornamented with numerous granules, and sometimes spines. They have 

 a central mouth in the midst of the five radiating avenues below, and an excentric vent on 

 their dorsal disk. They are all of a depressed form, and their ray and body-margins are 

 bordered by two series of large plates, forming their edges. The suckers in their avenues 

 are ranged in two rows. 



1. Goniaster Stokesii. Plate IV, fig. 6. 



Goniaster Stokesii, Forbes. Mem. Geol. Survey of Great Britain, vol. ii, pt. 2, p. 4/5. 

 Fig. and Descr. of Brit. Org. Rem., dec. i, pi. 3, fig. 1. 



Next to the Astropecten crispatus, this is the commonest of the species of star-fishes of 

 which remains occur in the London Clay of Sheppey. It has never, however, been found 

 in a perfect condition, and it is just possible that more than one species may be 

 confounded under the name. 



The general form appears to have been that of a pentagon, with greatly produced and 

 slender angles. The upper surface was covered by unequal polygonal ossicles, all 

 punctated for the insertion of minute granules. The edges of the body and rays were 

 bounded by a double series of cuboidal, stout, steep-sided marginal plates, with very 

 obtuse and gibbous, but not spiniferous or truly tuberculated angles. The surfaces of 



