9 
vertex. These are considered as included in two divisions ; Cidaris 
(the turban), and Clypeus (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. 
Fiom 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 
particular notions which have been entertained respecting their origin. 
Thus they obtained the name of ombria, from the Greek word 6^, 
signifying the heavy rain, in which they were supposed to fall; 
brontia, from fyovry, the thunder, by which they were supposed to be 
thi own to the earth ; ceraunii lapides, from xsfuwo;, the lightning, by 
which they were supposed to be generated and formed in the air; 
chelomtes, 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 
tubercles between the ambulacra. This species appears to have been 
1 are y found fossil ; it having been described, in this state, only by 
Aldrovandus, Mas. Metal, p. 456 ; and by the editors of the description 
of the museum of Moscardo, Mas. Moscardi, Lib. n. p . i;;. 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. saxalilL 
chiefly differs from the preceding, in its ambulacra being narrower, 
and m its being smaller, and of a more depressed form. It is supposed’ 
von. hi. 5 
V 
