9 



vertex. These are considered as included in two divisions ; Cidaris (the 

 turban), and Clipeus (the buckler). 



The first natural family in which these bodies may be placed, appears 

 to be that of Cidaris. The characters are : hemispherical, globular, or 

 suboval; with porous ambulacra, diverging equally, on all sides, from 

 the vent to the mouth ; vent vertical, mouth beneath and central. 



These, from their rounded forms and their different protuberances, 

 are supposed to resemble turbans, beset with their several ornaments. 

 From other characters, derived from their spines, they have obtained 

 the name of sea-urchins, sea-hedgehogs, sea-thistles, &c. and, those in 

 a petrified state, have obtained various names, agreeable to the par- 

 ticular notions which have been entertained respecting their origin. 

 Thus, they obtained the name of ombria, from the Greek word o^fyog, 

 signifying the heavy rain, in which they were supposed to fall ; brontia, 

 from fyovTy, the thunder, by which they were supposed to be thrown to 

 the earth ; ceraunii lapides, from xegawog, the lightning, by which they 

 were supposed to be generated and formed in the air ; chelonites, from 

 their resemblance, in their sutures, to the shells of the tortoise ; and 

 ova anguina, from their having been even considered by some as the eggs 

 of serpents. 



Of the fossils belonging to this family, the first species is Cidaris 

 esculenta\ which is hemispherical, with small, nearly equal sized tu- 

 bercles, between the ambulacra. This species appears to have been 

 rarely found fossil; it having been described, in this state, only by 

 Aldrovandus, Mm. Metal, p. 456 ; and by the editors of the description 

 of the museum of Moscardo, Mus. Moscardi, Lib. n. p. 177; and of 

 Calceolarius, Mus. Calceolarii, p. 412. A near approach to this echinus 

 is, I think, to be seen in the beautiful fossil from France, Plate I. Fig. 2, 

 from the late Mr. Forster's collection. C. saxatilis chiefly differs from the 

 preceding, in its ambulacra being narrower, and in its being smaller, 

 and of a more depressed form. It is supposed, by Leske, to have been 

 frequently found fossil ; he believing it to be figured as a fossil by Plot, 



VOL. III. C 



