Dr. T. Wright on the Oidaridtt of the Oolites. 167 



nodermes Fossiles.' Mr. M'Coy catalogues this species from the 

 Great Oolite of Minchinhampton, but we know of no specimens 

 from that locality ; all the examples, five in number, examined by 

 us, have been obtained from the upper beds of the Inferior Oolite. 



Genus Echinus, Linnaeus. 



Test more or less globular. Ambulacra in general about half 

 the width of the interambulacra ; primary tubercles of nearly the 

 same size in both areas, and forming vertical ranges more or less 

 numerous in the different species, but neither having perforated 

 summits nor crenulations at their base ; the poriferous avenues 

 are well-developed ; the pores are numerous, and disposed in 

 transverse ranges in arched or triple oblique pairs ; the mouth 

 is large, of a circular or pentagonal form, and more or less 

 divided at the margin by notches into ten lobes. The apical 

 disc is composed of four nearly equal-sized ovarial plates, and a 

 single larger madreporiform plate, and between the ovarial the 

 five ocular plates are lodged. The masticatory organs or lantern 

 are formed as in the genus Cidaris ; but the pyramids are exca- 

 vated in their superior part, and the two branches are united by 

 an arch at the summit. The teeth are tricarinated. 



Echinus perlatus, Desmarest. PI. VI. fig. 1 a, b, c, d. 



Syn. Echinus perlatus, Desm. Diet. Sc. Nat. t. xxxvii. p. 100. 

 Echinus lineatus, Goldf. Petrefact. Germanise, t. 40. fig. 11. 

 Echinus germinans, Phillips, Geology of Yorkshire, pi. 3. fig. 15. 

 Echinus perlatus, Agassiz, Echin. Foss. dela Suisse, t. 22. fig. 13-15. 

 Echinus diademata, M'Coy, Ann. Nat. Hist. vol. ii. S. 2. p. 410. 

 Echinus multigranularis, Cotteau, Echinides Foss. del'Yonne, p. 61. 

 tab. 7. fig. 6-8. 



Test hemispherico-conoidal with a pentagonal circumference; 

 ambulacral areas with two ranges of primary tubercles ; inter- 

 ambulacral areas furnished with two complete ranges of primary 

 tubercles and six incomplete ranges of secondary tubercles, 

 and a median depression in the centre of the areas ; apical 

 disc small ; anus eccentrical. 



Height 1£ inch, transverse diameter 2 inches. 



Description. — The ambulacral are about one-half the breadth 

 of the interambulacral areas, and are very uniform in width 

 throughout ; they are prominent and convex, giving the cir- 

 cumference of the test of this beautiful Urchin a pentagonal 

 form. The ambulacral columns have two rows of primary 

 tubercles, about thirty in each row, placed on the poriferous 

 borders of the plates, and from four to six tubercles between 

 thfert rows at the base and angle of the test. The interambu- 



