UPPER, OR FLINTY CHALK. 191 



from the preceding. The specimen figured is a siliceous cast, of which 

 fig. 16 is a profile, and fig. 19, a sketch of the base. 



LocaHties. Upper chalk, and ploughed lands near Lewes. 



37. Conulus vulgaris. Org. Rem. Vol. iii. PI. 2, fig. 3. 



The siliceous nucleus figured by Mr. Parkinson under this name is 

 from Sussex, but it appears to have been too imperfect to admit of its 

 characters being accurately defined. 



LocaUty. Upper chalk, near Lewes. 



38. Conulus subrotundus. Tab. xvii. figs. 15. 18. 



Subglobose, divided by biporous ambulacra into five wide and five nar- 

 row area ; mouth small ; vent placed in the margin. 



This species is somewhat globular ; the summit rounded, and rather 

 depressed; the base flat; the mouth circular; the vent eUiptical, and 

 placed in the margin. The surface is studded with granule. 



Figs. 15, 18, are different views of a siUceous cast collected near 

 Mount Caburn, by my friend Thos. Woollgar, Esq. ; the shell itself has 

 but lately been discovered. 



Localities. Upper chalk, near Lewes. 



EcHiNocoRYs (the helmet). Body vaulted, or helmet-shaped ; base 

 nearly flat ; mouth and vent beneath, and opposite. 



39. Echinocorys scutatus. Org. Mem. Vol. iii. PI. 2, fig. 4. 

 Galeated, with a prominent ridge extending from the vertex to the 



vent ; surface granulated, divided into five small, and five large are£e, by 

 biporous ambulacra ; base oval, with the vent placed near the margin of 

 its longest diameter ; mouth transversely reniform, situate at the broadest 

 extremity, with a ridge passing from it to the base. 



This species is found in great numbers in the vicinity of Lewes, and 

 Brighton, and siliceous casts deprived of their calcai'eous covering, are 

 very common among the flints of the Downs. 



The cavity of the shell is generally filled with chalk, or flint, but in a 

 few instances is partly hoUow, and its inner surface hned with transparent 

 crystals of carbonate of hme ; these in all probability have been formed by 

 an infiltration of calcareous spar through the substance of the shell, sub- 



