46 



The echinite found by M. de Luc was calcareous, but filled with 

 and imbedded in flint. Another specimen, very nearly similar to 

 the foregoing, is figured and described by Andrea, Lit. Helvet. p. 267. 

 This specimen was found in the mountain named Randerberg, . in Swit- 

 zerland. A specimen of this kind, in flint, from Kent, is represented 

 Plate IV. Fig. 21, with one of the spines lying close to the papilla on 

 which it had been fixed. In this specimen may be seen the characters 

 of the echinus. This, it is evident, is a species of Cidaris papillata ; but 

 differing from any which has been described, in having the articulations 

 of the assulse much more concealed by the granular surface, which is 

 extended from papilla to papilla. In another specimen, Plate IV. Fig. 1, 

 in chalk, four of the spines are still adherent; and in another, in which 

 several spines and two of the larger arese are imbedded in chalk, the 

 particular character of this shell is also plainly manifested. In another 

 flint specimen from Pangbourn, in Berkshire, the spine is somewhat dif- 

 ferent, the longitudinal grooves being deeper, and the denticulse more 

 distinct. 



The origin, therefore, of the Lapides Judaici, or petrified olives, as 

 these stones were formerly considered, is therefore now determined ; 

 and the species of echinite also, to which they belong, is completely 

 ascertained. 



I am indebted to that accurate observer of nature, Mr. Sowerby, for 

 a very ingenious suggestion, as to the cause of a peculiar variety of 

 figure which sometimes occurs in these spines. They are sometimes seen 

 more than usually tumid and irregularty rugose : this he imputes, and I 

 am assured of his being right, to the spine having suffered from disease. 



The second species, Cucumerina, is divisible into several varieties, in 

 which, although the cucumber form is preserved, very considerable 

 differences are observable. In some, the surface is neither striated nor 

 granulated ; but irregularly and slightly nodular. But the surface in 

 general possessed by these bodies, is formed by small granular or denti- 

 culated projections, disposed in regular rows. Plate IV. Fig. 2, 6, 8, 15, 

 16, and 17. 



