108 



FOSSIL OOLITIC ASTERIADtE. 



The upper and under surfaces of the disc are covered with a kind of Mosaic composed 



of small tetragonal or polygonal os- 

 ^^^- ^^' sides united by a delicate mem- 



brane ; these plates are not firmly 

 articulated together, and they are 

 consequently easily displaced, so that 

 they are rarely preserved in a fossil 

 state. The ossicula of the disc and 

 margin usually support small granular 

 spines, and sometimes sessile pedi- 

 cellarige. The ambulacral furrows are 

 bordered by square ossicula, and the surfaces are marked by deep parallel grooves which 

 serve for lodging the ambulacral spines (fig. 35 </). The marginal plates towards the 

 termination of the rays are modified and enlarged for supporting and protecting the eyes 

 (fig. 35 d). 



A. — Species from the Inferior Oolite. 



GoNiASTER OBTUSus, Wright. PI. II, fig. 3 «, <5, 3 e, 3 d. 



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



Rays elongated, rounded at the extremity ; marginal plates convex and prominent, the 

 upper row larger than the under, the entire surface of both plates covered with fine 

 granulations ; a single row of small polygonal plates between the upper marginals, the 

 ocular plate at the end of the ray prominent. 



The fragment above described is the largest portion of a Gonioster I have collected 

 from the Pea Grit, Inferior Oolite. I have frequently obtained individual bones belonging 

 to the marginal skeleton of this genus, but the conditions under which this deposit was 

 accumulated appear to have been unfavorable for the conservation of the entire body. This 

 fragment proves, however, that the Goniasteriad^ appeared with the dawn of the Jurassic 

 epoch along with many new forms of Echinodermata in the seas that deposited the first 

 oolitic sediments. 



I found associated with this Star-fish Gdaris Fowleri, Wr., C. Bouchardii, Wr., 

 C. Wrightii, Des., Stomechinm germinans, Phil., Pseudodiadema depressum, Ag., Polycyphus 

 Deslongchampsii, Wr., Pedina BaJceri, Wr., Hemipedina perforata, AVr., together 

 with Galeropggus agariciformis, Forb., and Pygaster semisulcatus, Phil., in considerable 

 numbers. 



