FROM THE INFERIOR OOLITE. 375 



Section B. Anal valley does not extend from the border to the disc. 

 A. Species from the Inferior Oolite. 

 Clypeus Hugh, Agassiz. PL XXX, fig. 1 a, b, c, d, e,f. 



Clypeus Hugh. Agassiz, Echinodermes Foss. de la Suisse, 1' Partie, tab. x, fig. 



2—4, p. 34, 1839. 



— — Agassiz and Desor, Cat. rais. des Ech. Ann. Sc. Nat., 3 serie, 



torn, vii, p. 156, 1847. 



— — D'Orbigny, Prod, de Pal. Strata, t. i. p. 290, No. 496, 1850. 

 NucLEOLiTES HuGii. Forbes, Mem. of the Geol. Surv. of Great Britain, Decade i, 



description of PL ix, 1850. 



— — Wright, Ann. and Mag. of Nat. Hist. 2d series, 1851, vol. ix, 



p. 303. 



— — Forbes, in Morris's Catalogue of Brit. Fossils, p. 84, 1854. 

 Clypeopygus Hugh. Desor, Synopsis des Echinides Fossiles, p. 274, 1857. 

 EcHiNOBRissus HuGii. Cotteau and Triger, Echinides du departement de la Sarthe, pi. vi, 



fig. 10—12, p. 58, 1858. 



Test sub-orbicular, dorsal surface convex; apical disc central; ambulacral areas 

 narrowly petaloid in the upper two thirds of the dorsal surface ; anal valley short, and 

 wide, occupying the lower half of the area ; a considerable portion of undepressed test 

 between the disc and valley, single inter-ambulacrum produced and deflected; base 

 nearly flat, mouth-opening sub-central, nearer the anterior than the posterior border, 

 peristome pentagonal, surrounded by five oral lobes ; a penta-phylloid floscule around the 

 mouth. 



Dimensions. — Height, one inch ; length and breadth nearly equal, two inches and 

 one eighth. 



Description. — All the specimens of this urchin I examined before the fine example 

 figm'ed in PL XXX, were small, and resembled EcUnobrissus, but in this urchin the 

 characters of Clypeus are well marked ; the test is circular, being nearly as long as it is 

 broad ; it is rounded before (fig. 1 a), and slightly rostrated behind, by the prominence 

 and deflection of the single inter-ambulacrum (fig. 1 b) ; the upper surface is uniformly 

 convex (fig. 1 c), in the figured specimen it is rather conical, rising high at the vertex, 

 and declining rapidly on aU sides, more especially towards the posterior border ; 

 the base is flat or slightly concave, and the basal portions of the inter-ambulacra form 



49 



