6 



BRITISH FOSSILS. 



the figure given by M. Agassiz ; the published mould is quite 

 like our fossil " L'espace entre les deux series de gros tubercles 

 est parseme, comme dans I'espece precedente ( 8. petalifera)^ mais 

 en nombre moins considerable, de tres-petites granulations, qui ont 

 ete omises par erreur dans le dessin." 



The Cidaris acrocidaris, Portl., from the Irish Chalk, is a flint cast of 

 a small Salenia resembling that figured in Dixon's Geology of 

 Sussex, pi. 25, f. 25. It may be the cast of one of the un-named 

 species (of which there are several in the British Museum) found 

 in Scania and at Ciply. 



Locality. — This beautiful species occurs in the Chalk of the North 

 of Ireland, and, very rarely, in the Upper Beds op Chalk at 

 Norwich, and in Sussex. It is also found at Havre. Flint casts 

 are not uncommon in the gravel of Norfolk. 



5. S. clathrata, Ag., MS. Morris's Cat., 2nd ed., p, 89. 



Body subglobose, very convex above ; lat. 6, alt. 4^ lines ; apical disk 

 lat. 5i lines, nearly covering the upper surface, its outline very deeply 

 indented between the ocular and genital plates ; anal opening with a very 

 prominent margin ; plates smooth, deeply notched at the sutures, those 

 connecting the centres of the plates forming a distinct pentagon, and each 

 of the genital pores is the centre of five radiating grooves, with angular 

 pits between ; ambulacra narrow ; tubercles few and prominent, separated 

 by a narrow miliary zone. 



The smallest specimens found at Warminster are very gibbous, and 

 appear to be dwarfs, rather than young individuals. The species 

 attains a large size in the Grey Chalk, and are occasionally more 

 depressed, with the marginal lobes of the anal disk broader, and 

 the sutural grooves less excavated. The name S. umbrella (Ag., 

 MS.) appears to have been intended for those specimens with the 

 sutural grooves most deeply and sharply defined. The figure in 

 Parkinson's Organic Eemains (vol. iii. pi. 1, f. 13), referred to by 

 Prof. Forbes, in Decade I., as " S. ornata, Ag. MS.,'^ is indeter- 

 minable. 



Locality. — Upper Green Sand, Warminster; Grey Chalk, Dover. 



6. S. Bunburyi^ Forbes, MS. Morris's Cat., 2nd ed., p. 89. 



Body subglobose, tumid above, with a wide base, and depressed oral 

 aperture ; lat. 7, alt. 5^ lines ; apical disk, 5^ lines in diameter, vent 

 with a prominent thickened border, plates sculptured at the border of 

 the disk, sutural notches forming deep linear grooves (as in S. umbrella) ; 

 ambulacra narrow, sinuous, with small remote tubercles divided by a 

 prominent granulated ridge ; interambulacral tubercles 4, 5, prominent, 

 divided by a wide miliary tract. 



Locality. — Lower Chalk, Mildenhall, near Bury St. Edmunds. The 

 original and unique specimen in the Mus. Pract. Geol. was pre- 

 sented by E. H. Bunbury, Esq., M.P. 



