3IES0Z0IC R A 1)1 AT A. 61 



height G lines), margin obtusely rounded ; mouth one-third the 

 diameter of the disc ; anus small, pyriform, marginal extending 

 as much above as below, its own width distant from the mouth ; 

 about six rows of primary granules in the ambulacral and 

 fourteen in the interambulacral spaces. 



The only other oolitic Discoidea I know with a marginal anus 

 is the D. hemisphcerica (Ag.), from which this differs in having 

 the anus even more remote from the mouth, the mouth larger, 

 the granules more numerous and smaller, and above all by the 

 form being even more depressed than that of the D. depressa 

 (Linn. sp.). 



Very abundant in the inferior oolite of Bridport. 



(Col. University of Cambridge.) 



Py g aster suhlcevis (M'Coy). 



Sp. Char. Orbicular, margin of the posterior interambulacral 

 space more convex than the others ; much depressed (length 2 

 inches 4 lines, width 2 inches 6 lines, depth 10 lines) ; vertex 

 central ; anal furrow deep parallel-sided, becoming gradually 

 fainter towards the posterior margin ; surface of oral disc un- 

 dulated by the gentle convexity of the interambulacral spaces 

 and the depression of the ambulacra; mouth only about one- 

 seventh of the diameter, rather nearer the anterior than the 

 posterior margin; granulation on the dorsal aspect so fine 

 that the surface seems smooth or nearly so to the naked eye, 

 abruptly increasing in size on the oral disc and margin, where 

 however four of the primary tubercles only occupy the space 

 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- 

 peuSf 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 hrevifrons (M'Coy). 



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

 width 3 inches 3 lines, height I 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- 



