BRITISH FOSSILS. 



Decade I. Plate III. 



TERTIARY (EOCENE) SPECIES Of GONIASTER. 



[Genus GONIASTER. Agassiz. (Sub-kingdom Radiata. Class Echiuodermata. Order 

 Asteriadse. Family Goniasterise). Body pentagonal ; a vent on the dorsal surface ; disk 

 much depressed, fiat when dead ; skeleton composed of tessellated plates, variously studded 

 with granules, spines, and in many instances, pedicellarifE ; rarely naked ; margins 

 bounded by two series of large plates ; suckers biserial.] 



Fig. 1. 

 GONIASTER STOKESIl^ 



E. Forbes, in Memoirs of the Geological Survey of Great Britain," 

 vol. ii. part 2, p. 475. 



Diagnosis. G. corpore pentagonali, angulis longe pfoductis^ lateribus 

 profunde lunatis: ossiculis lateralibus superioribus disci oblong o-quadratis 

 depressis eu convexiuscuUs^ brachialibus quadratis tumidis, extrorsum 

 abruptis ; omnibus punctatis^ inferioribus similaribus. 



Description. — Although I have never met with this very distinct 

 species in a perfect condition, numerous fragments of greater or less 

 dimensions give a very perfect notion of its size, form, and proportions. 

 The body was pentangular, with angles greatly produced, and even 

 attenuated at their extremities (fig. 1, a. and d^ into linear parallel- 

 sided arms. The disk was flat, and, as well as the arms, bordered by a 

 double series of subquadrate, steep-sided, somewhat nodular, nearly 

 equal, thick marginal plates, the sides of which are quite equal in dimen- 

 sions to the summits (fig. 1, b. and c). These plates are coarsely but 

 rather regularly punctated on their exposed surfaces. Their prominent 

 nodular summits seem often as if subtruncated. The nodular convexity of 

 each plate is placed towards its marginal extremity. The summits of the 

 superior plates are more prominent than those of the inferior. Towards 

 the prolonged extremities of the arms these nodulations begin to dis- 

 appear ; but the plates are always highly convex in their centres, so as 

 to be strikingly distinct from each other, and to seem as if separated by 

 a deep sulcus. The extremities of the rays are slightly swollen. They 

 terminate in a distinct small semicircular ocular plate, bordered on each 

 side by two (transformed marginals) small oblong oculars. The surface 

 [i. iii.] D 



