39 



Fig. 20, spines of the same class are fixed. But these appear to have 

 been longer, and more of a cylindrical form than those above described. 



[n a fossil from Hertfordshire, in which an echinite, probably of the 

 variolated kind, is involved in a mass of pyritous clay, innumerable subu- 

 lated and capitated aciculae are seen piercing through and laying in the 

 surface of the mass. 



The capillary aciculre are so small as to give but little chance of detect- 

 ing them, mineralized, in an attached state ; and I know but of one instance 

 in which they have been found petrified arid adherent. This has lately 

 occurred in a mass of silicious cordated echinites from Devonshire, im- 

 bedded in a matrix of chert. In this specimen, the capillary acicular 

 spines are accumulated on the echinites, in prodigious numbers. 



The spines comprised in the class of SUDES are very numerous; but, for 

 the reasons already related, the spines of this class, in the state of petrifac- 

 tion, are very rarely found in attachment with their shell. The first 

 genus of this class, Sudes villarum, Stakes, is divided into three species : 

 1. lavis; 2. nodosa ; 3. granulate and striata ; 4. torosa, Kc. Of the first 

 of these species, I have not, to my recollection, seen a specimen ; the 

 glass making some configurations appear on the surface of all which I 

 have examined of this genus : nor have I seen any of the second spe- 

 cies, simply knobbed, the lens generally showing striae also. 



Of the third species, granulated, there exist many varieties; among 

 which, indeed, are several, apparently deserving of being considered as 

 distinct species. Plate IV. Fig. 3, represents a cylindrical species, with 

 denticulated rings, which is adherent to its shell, by which we discover 

 that it belongs to one of the Cidarcs papillata. This spine is capitated ; 

 and, if it were not in a slight degree tumid at its commencement, might 

 be considered as completely cylindrical. It is surrounded by eight rows 

 of denticulated granulae, the surface between which is minutely striated. 

 In one specimen which I possess, these spines, very little superior, as to 

 thickness, to those which are here represented, are full five inches and a 

 half in length. 



