12 



as a fossil, and is figured by Rumphius, Amb. PL LIX. Fig. c. and by 

 Breynius, p. 55, who names it Echinometra Circinnata. 



The chalk specimen, Plate I. Fig. 10, from Kent, does not sufficiently 

 agree with any species with which 1 am acquainted, to allow of its being 

 supposed to be exactly analagous. It may, however, be considered as 

 belonging to this genus (variolata.) 



The third genus of Cidaris is C. mammillata. The first species of this 

 genus is distinguished by Leske by the name of the genus, and figured 

 by Klein, Tab. vi. A. B. c. D. The shell of this species is elliptical and 

 depressed. The areae are, five large, and as many small, beset with 

 papilla?, not perforated, and of a size proportioned to the areae: the 

 ambulacra are singly porous. This species is not very common in a fossil 

 state. The fossil referred to by Leske, in Bourguet, Fig. 337, is cer- 

 tainly of this species ; but that of Lister cannot be spoken of so deci- 

 dedly. 



The next species, C. papillata, Lesk. and E. cidaris, Lin. the moorish 

 turban (cidaris mauri), is round in its circumference, and rather de- 

 pressed. It has five areae, on which are alternately disposed two rows 

 of mammilla?, each of these being surmounted by a perforated papilla, 

 crenulated at its base, and surrounded by a distinct groove : the rest of 

 the area being filled by minute puncta and granular projections. Each 

 papillary tubercle of this echinus has its own plate. Between each pair 

 of ambulacra, which are biporous and undulating, is a narrow granu- 

 lated band : these are considered by Leske as the less area?. 



Petrified specimens of this species have been frequently figured and 

 described. These are, the ovi anguini of Pliny, and the brontix. of Agri- 

 cola. They are also figured by Plot, Hist, of Oxfordshire, Tab. v. Fig. 3, 

 4; and copied by Lister, lap. turb. Fig. 22 and 25. Lhwydd, Tab. 12, 

 Fig. 910, has depicted a fragment; and Morton, two complete speci- 

 mens, Hist, of Noi'thumberland, T. 10, /. 3, 5. Representations also, of 

 this species, are seen in most of the works of the foreign oryctologists. 



In the figures given by Drs. Plot, and Lister, considerable difference is.. 



