MESOZOIC RADIATA. G3 



narrovV; gradually enlarging towards the margin, posterior pair 

 double the width of the anterior ones, short, curved, meeting 

 immediately over the anus. 



If carefully observed, this can only be confounded with the D. 

 ringens (Ag.) of the Swiss oolites, but it is at once distinguished 

 by its greater gibbosity (in which it exceeds the allied D. Voltzii) 

 and in the less prominence of the ridges on the under side, which 

 however exceed those of the latter species ; the disproportionate 

 narrowness of the three anterior ambulacra, as in the 1). ringens, 

 separates it from the D, Voltzii and D. Eudesii (Ag.). 



Not uncommon in the inferior oolite of Dundry and Leek- 

 hampton. 



{Col. University of Cambridge.) 



Nucleolites planulatus (M^Coy). 



Sp, Char. Rotundato-subquadrate, length and width equal, much- 

 depressed, upper surface flattened, margin obtusely rounded 

 (length and width 1 inch 3 lines, depth 6 lines) ; ambulacra 

 wide, the pores of each pair in the petalloid part connected 

 by a long distinct furrow ; anal sulcus deep, extending from 

 the vertex to the anal margin which it slightly indents ; gra- 

 nulation very minute. 



This species from its great depression need only be compared 

 with the N. planatus (Romer, Versteinerungen des norddeutsch. 

 Oolithengebirge), but it is wider than that species and the upper 

 surface flatter, and I find on comparing specimens of the two 

 species that the present is completely distinguished by its wide 

 ambulacra and the very distinct sulcus connecting the pores of 

 each pair ; the ambulacra of the former species being narrow and 

 the pores unconnected. 



Common in the coralline oolite of Malton. 



Rare in the great oolite of Minchinhampton. 



{Col. University of Cambridge.) 



Nucleolites pyramidalis (M'Coy). 



Bp. Char. Base obtusely cordate or rotundato-quadrate, width 

 equalling or slightly exceeding the length, much elevated to a 

 nearly conical apex which is slightly nearer the anterior than 

 the posterior end (length and width 1 inch 2 lines, height 8 

 lines) ; a deep narrow sulcus extends from the vertex to the 

 posterior margin ; petalloid ambulacra of moderate width, the 

 pores of each pair united by a strong sulcus ; upper surface 

 not very tumid, but rather pyramidal, of four slightly flattened 

 sides; profile, anterior end slightly convex, posterior face longer, 

 forming a steeply inclined plane from the pointed vertex to the 



