16 



composing the shell, and of the sutures by which these are connected, 

 depending merely on the thickness with which the tubercula are dis- 

 posed, and on the bowldered state of the shell, cannot be regarded as 

 even a specific distinction. 



Of the several species placed by Klein under this assumed genus, none 

 have been noticed as fossils, except C. Sardiaca, Klein, Tab. ix. A. B. by 

 Scilla, Tab. xvi. Fig. 1, and Tab. xxvi. Fig. B. ; C. Botryoides, Klein. 

 Tab. xi. H. by Aldrovandus, Mus. Metal, p. 457 ; and C. Toreumatica, 

 Klein. Tab. x. D. E. by Leske, Tab. XLIV. Fig. 2. 



I cannot introduce the necessary notice of the Echinites favagmeus in 

 any better place, I presume, than this. The echinites thus named bear 

 on their surfaces hexagonal cavities, which give to the fossil somewhat 

 of the appearance of a honeycomb. These fossils have been noticed by 

 Encelius, Wormius, Olearius, Oliger, Jacoba3us, and others; but with- 

 out any rational conjecture having been offered as -to their nature and 

 origin, until the attention of M. Walch was attracted by a very beau- 

 tiful specimen, and his ingenuity was exercised in its examination, Mo- 

 numens des Catastrophes, Tome II. Sect. 1, p. 155. This fossil he describes 

 as a crystallized cast of an echinite, composed of hexagonal cells, resem- 

 bling those formed by the bee. These cells, he observes, agree exactly 

 in their margins with the shape of the plates of the echinus, with which 

 they also agree in their general form ; and hence he infers, that the su- 

 tures, by which the plates were connected, had influenced the formation 

 of these hexagonal cells. 



In answer to the inquiry, in what mode is this influence exerted, 

 M. Walch remarks, that the cavity of the shell being filled by any crys- 

 tallizing fluid, the first formation of crystals would be, that which would 

 fill up the small spaces existing at the articulation of the plates ; and 

 thus would be formed the bases, or margins, of these hexagonal co- 

 nical cells. These being formed, he thinks, on the principle that 

 homogeneous particles are most likely to unite, that the successive ap- 

 proximation of crystallizing particles will take place on these hexagonal 



