414 Mr. F. M'Coy on some new Mesozoic Radiata. 



of one line ; in a transverse row there are nine or ten in an 

 ambulacral and upwards of fifty in an interambulacral space. 



In its depression, the shape of its anal sulcus, and the undu- 

 lation of its base and small mouth, this species resembles a Cly- 

 peus, but the structure of its ambulacra, &c. is strictly that of 

 this genus. Its nearly smooth surface, resulting from the very 

 small size and prodigious number of the primary tubercles, di- 

 stinguishes it from its congeners. 



Common in the inferior oolite of Leckhampton. 



(Col. University of Cambridge.) 



Pygaster brevifrons (M'Coy). 



Sp. Char. Subpentagonal, much elevated (length 3 inches 2 lines, 

 width 3 inches 3 lines, height 1 inch 8 lines) ; posterior mar- 

 gin slightly less convex than the others ; anus large, pyriform, 

 close to the vertex, which is nearer to the anterior than to the 

 posterior margin, so that in the profile the anterior side is con- 

 siderably shorter and more steeply inclined than the posterior ; 

 mouth small, deeply impressed ; primary tubercles large, scat- 

 tered. 



This species in size and form of the base resembles the P. um- 

 brella (Lamk. sp.) (Clypeus semisulcatus, Phil.), but is more ele- 

 vated ; and while in the profile of that species the posterior side is 

 much the shortest and most highly inclined, the proportions of 

 the present fossil are precisely reversed, a character which also 

 separates it from the other known species. The tuberculation is 

 as large, but more scattered than that of the P. patelliformis (Ag.). 



Not uncommon in the inferior oolite of Dundry. 



(Col. University of Cambridge.) 



Dysaster symmetricus (M'Coy). 



Sp. Char. Regularly oval (length 10 lines, width 8^ lines, depth 

 6^ lines), anterior and posterior ends equal in size and con- 

 vexity, neither of them sinuate ; uniformly gibbous, except a 

 small subangular prominence at the apex of the anterior am- 

 bulacrum, and the middle of the base which is slightly con- 

 cave, the margin of the base being obtusely rounded except in 

 front of the mouth where it is concave — it is most tumid at the 

 opposite end ; mouth small, rather more than one-third of the 

 length from the anterior end ; anus high on the posterior face, 

 the shell beneath is not sinuate, evenly convex ; ambulacra of 

 moderate and nearly equal width, the posterior pair meet just 

 over the anus, the anterior one does not quite reach to the 

 other two, the point of convergence of which is two-fifths the 

 length of the shell distant from that of the posterior pair. 



