Mr. F. M'Coy on some new Mesozoic Radiata. 413 



having a few crowded granules between the rows but no se- 

 condary tubercles ; there are only five or six pairs of ambu- 

 lacral pores disposed in the single part of the row, rather be- 

 low the middle, above which the pairs of pores are in regular 

 double rows, each pair being separated by a diagonal line; 

 below the single part of the ambulacra the pairs are in irre- 

 gular double series increasing to three rows near the mouth. 



This differs from the Diadema [Diplopodia] subangulare (Ag.) 

 in its more depressed and distinctly pentagonal form, in the very 

 short single portion of the ambulacra, there being nineteen or 

 twenty pairs of pores in a single vertical row in the middle of 

 that species, and in the deficiency of secondary tubercles along 

 the margin of the interambvdacra. 



Not uncommon in the great oolite of Minchinhampton. 



{Col. University of Cambridge.) 



Discoidea marginalis (M'Coy). 



Sp. Char. Nearly circular, depressed (length and width 1 inch, 

 height 6 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.) 



Pygaster suhlaevis (M'Coy). 



8p. 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 



