4 



BRITISH FOSSILS. 



three fifths of the whole diameter. The notches are placed in pairs 

 at the oral edge of the interambulacral spaces, their depth being 

 about equal to their width apart, and those of each pair are con- 

 siderably nearer to one another than to the neighbouring pair. 



Our specimens shew no spines. They are, however, represented 

 by Prof. Agassiz in the Ech. Suisses, t. 17- £ 51., as slender, cylin- 

 drical, solid, pointed at the ends, and finely striated. 



Affinities, — There seems to be no other English species with 

 which it can be compared, unless a somewhat more convex and 

 smaller form which is said to occur with it in the Malton Oolite may 

 be considered distinct. This species or variety has fewer (twelve) 

 and rather more prominent interambulacral tubercles, and the secon- 

 daries between these are smaller and fewer. The ambulacra are a 

 trifle narrower in proportion, and are somewhat more convex than 

 the intervening spaces, while in the figured species there is no such 

 difference ; and as the primary tubercles are not so crowded in the 

 rows, they are rounder and less oval than in D. pseudodiadema. 

 The apical disk is very much the same, but there is a difference in 

 the arrangement of the pores near the mouth, which can scarcely 

 be due to age — only about eleven or twelve pairs of pores (instead 

 of twenty) being formed into ranks of threes. Specimens of this 

 in the British Museum and the Geological Survey Collections 

 agree with D. hemisphcBricum, Ag., as figured by Cotteau, and are 

 in all probability French specimens from the Coral Kag. 



On this species Prof E. Forbes left a good many notes, which are 

 embodied in the above description, and his views of the synonymy 

 are correctly expressed here, as also in the second edition of 

 Morris s Catalogue. He has quoted in his MSS. the reference to 

 D. Lamarcldi of Desmoulins (which Dr. Wright adopts) with a 

 doubt, and remarks of Cotteau's figure, " that it represents a cast, 

 and is not good in its details. The pores are especially confused. 

 Unaccountably, too, perhaps by the erroneous drawing of the pores 

 in Phillips's figure, Cotteau has referred Echinus germinans of 

 Phillips ( E, perlatus of this Decade) to his species.'' Agassiz and 

 Desor, in the Cat. Eais., have done the same, though with a mark 

 of doubt. The D. amhiguum of Desmoulins, according to these 

 authors, is a synonym of the present species. 



Locality and Geological Position. — Cokal Eag. Malton, near 

 Scarborough. 



Foreign Localities and Range, — "Corallien" of Besancon, 

 canton de Soleure; St. Mihiel; La Bochelle. 



J. W. Salter. 



January 1856. 



