8 



BKITISH FOSSILS. 



14. D, Bonei, Forbes, Morris's Catal., 2nd edit. 1854. 



Circular or slightly pentagonal, depressed ; lat. 9, alt. 4 lines ; base rather fiat; 

 ambulacral tubercles rather prominent, as large as the interambulacral, in 2 rows of about 

 10 each, close together, separated only by a zigzag line of small granules ; interambulacral 

 tubercles also in 2 rows of 10 each, with accessory rows of about 6 small tubercles outside. 

 This urchin agrees with a specimen from M. Michelin, labelled (erroneously) " X>. sub- 

 nudum, Villers sur Mer ; " it is perhaps the D. Michelini, Desor, Synopsis, p. 72. 



Locality. — This species is rather less abundant than Z>. BenetticB in the Upper Gkeen 

 Sand of Warminster, and never attains an equal size. It has a more spinose appear- 

 ance, owing to the closer approximation of the ambulacral tubercles. 

 Note. — D. rotatum, Eorbes, 1. c, is the Ci/phosoma difficile, Ag., and D. M^Coyi, Forbes, 

 (Z>. rotularc, M'Coy, not Ag.), does not differ from it in any respect.* 



15. D. Ehodani, Ag., Ech. Suisses, t. 16. f. 16-18. 



Locality. — "Upper Green Sand, Blackdown, M'Coy," (Morris's Catal. p. 77.) 

 The locality requires confirmation. 



1 6. D. Desori, Forbes. (Syn. B. Ehodani, Ag. ?) 



Circular, depressed, convex above, concave beneath ; lat. 10, alt. 4,j lines ; apical disk 

 small (lat. 3^ lines), pentagonal ; ambulacra sinuous ; tubercles in two rows of 1 0 or 1 1 

 each in all the divisions, those of the upper surface (3 of each row) minute, with very 

 small bosses and areolae, the interspaces minutely and uniformly granulated ; marginal 

 ubercles 2 or 3 in each row, large and prominent ; base with accessory rows of tubercles 

 on each side, and in the centre of each division ; the whole small, subequal, and closely 

 ranged. 



The solitary specimen in the Museum of the Geological Survey, upon which this 

 species was founded, was at first identified with D. Ehodani, Ag., but afterwards, 

 probably with the approval of M. Desor himself, considered distinct. Compared 

 with Agassiz's figure, and with an authentic example of D. Ehodani in the Brit. 

 Museum, it differs in the size and form of the apical opening, and in the larger 

 number of small tubercles on the upper aspect, thus giving a greater extent of 

 uniformly granulated surface. Several other specimens in the collections of 

 Mr. Cunnington and Mr. Sloper of Devizes haye been examined, and show that 

 the species is liable to considerable variation. 



Locality. — Upper Green Sand, Warminster. 



17. D. pmtulatum, Forbes, 1. c. 



Sub-pentagonal, depressed, concave beneath, convex above, slightly inflated at the 

 angles; lat. 14, alt. 6 lines ; ambulacral tubercles in 2 distinct rows of 14 or 15 each, 

 with 3 rows of small accessory tubercles (5 or 6 in each) below ; interambulacral tubercles 

 13 or 14 in each row, with 6 accessory rows of small unequal tubercles beneath ; tubercles 

 largest at the circumference, becoming gradually smaller above and below ; areolae of 

 the upper tubercles very small, interspaces uniformly granulated. 



This species resembles M. Agassiz's figure of D. Ehodani even more than the last ; 

 compared with the specimen from the Perte du Rhone, it diflfers in the greater 

 number and regularity of the rows of tubercles, the wider space between the 

 ambulacral rows, the more densely granulated interspaces, and the greater number 

 of accessory tubercles beneath. It is to be feared that the discovery of more 

 specimens will not increase the validity of these differences. 

 Locality. — Upper Green Sand. (Craie chloritee), Chard stock. Presented to the 

 Mus. Pract. Geology by E. H. Bunbury, Esq., M.P. 



* It has been placed in the genus Glypocyphus by M. Desor (Syn. p. 1 04), from which 

 it differs totally in the character of its apical disk. 



