GONIASTER. 



109 



B.' — Species from the Great Oolite. 



GoNiASTEB Hamptonensis, Wright. PI. II, fig. 2. 



GoNiASTER Hamptonensis, Wright. British Association Reports, vol. for 1856, p. 402. 



Body pentagonal, sides arched, rays projecting in the form of cones, and tapering to a 

 point ; marginal plates thick, sides elevated, and inclined inwards ; upper surface of the 

 disc covered with small polygonal ossicles. 



Dimensions. — Diameter of the body from ray point to ray point, three inches; diameter 

 of the disc, from the inner side of one superior marginal plate to the same point of the 

 opposite margin, one inch and a quarter; depth of the border at the centre of the arched 

 side, three-tenths of an inch. 



Description. — The specimen figured in PI. II, fig. 2, is the only Goniaster which has 

 been found at Minchinhampton, It is unfortunately broken, and the portion preserved 

 is so much incorporated with the matrix, that the sculpture on nearly all the marginal 

 plates is destroyed. In the most perfect side, there are twenty-five upper marginal plates, 

 but the lower series cannot be counted. The margin is high, and inclined inwards 

 (fig. 2 t)). The five rays project like narrow cones from the sides of the disc, thereby pro- 

 ducing the arching of the margin so characteristic of this species (fig. 2r/). 



The upper surface of the disc was covered with small tetragonal or polygonal plates, 

 which have been so much effaced in carving out the fossil from the oolitic matrix, that 

 sections only of a few of them remain. On one or two upper marginal plates, I have 

 seen a finely granulated surface, whilst all the others are pitted by the oolitic grains 

 during the process of cystalhzation in the replacement of the test. 



Affinities and differences. — This oolitic species very much resembles some cretaceous 

 forms, as Goniaster Smithii and Goniaster Coomhii ; the form and structure of the marginal 

 plates, and the clothing of the upper disc appear very similar in both, there is no other 

 oolitic species at present sufficiently known with which it can be compared ; the mere 

 fragment of Goniaster ohtusus, Wr., from the Inferior Oolite, does not afford materials for 

 comparison. The fine-pointed termination of the rays in Goniaster Hamptonensis, Wr., 

 however, is very different from the blunted termination of the ray in Goniaster ohtusus, Wr. 



Locality and Stratigraphical jwsition. — This specimen was discovered by Mr. Edward 

 Day, many years ago, in the planking beds of the Great Oolite of Minchinhampton Common, 

 by whom it was cleared or rather carved out of the soft freestone in which it was imbedded ; 



