194 UPPER, OR FLINTY CHALK. 



and markings ; but the following are the only species that have been ob- 

 served in this district. 



44. Clavated spines. Tab. xvii. figs. 11. 14. 



These are dehcately muricated; they belong to a species of Cidaris, to 

 which Mr. Konig has appHed the name of C. claviger. 

 Locahties. Upper chalk, near Lewes, and Brighton. 



45. Cucumerine spines. Tab. xvii. figs. 12, 13. 



The elegant spine, fig. 12, is well known to collectors, and occurs in 

 great perfection in the hmestone of Calne, in Wiltshire ; it belongs to Ci- 

 daris sceptrifera (of Konig). The other specimen, fig. 13, has previously 

 been described as the spine of Cidax'is papillata'* . 



Locahty. Upper chalk, near Lewes. 



Testace^. 

 Univalves. 



46. Cnv\xQ perspectivus. Tab. xviii. figs. 12. 21. 



Obtusely conical; volutions convex, transversely ovate, spirally stri- 

 ated ; umbihcus deep, exposing one-third of the volutions ; aperture 

 transversely oblong. 



The umbilicus of this species resembles in structure that of the cele- 

 brated staircase shell, (Trochus perspectivus of Linne,) exposing the 

 inner edge of the volutions, to the extent of nearly one-third of their 

 width. The volutions are six or seven in number, convex externally, 

 smooth in the casts, but where portions of the shell remain, marked with 

 fine spiral strife. 



The specimens are seldom more than chalky casts ; vestiges of the 

 shell itself being exceedingly rare. A few examples have, however, been 

 noticed, in which the casts are covered with a nacreous peUicle, the remains 

 of the internal pearly coat of the original. 



Tab. xviii, fig. 12, represents the most perfect specimen in my posses- 



* The teeth of echini have been discovered in the chalk, near Brighton, and I remember 

 seeing several specimens, collected in the vicinity of that town, a few years since ; but I have 

 not been able to obtain a single example, either for description or representation. 



