446 CLASS ECHINODERMATA. 
Their teste are preserved in great abundance in ancient 
strata, especially those of the chalk formation, when they are 
usually filled with silex. 
The echini should be divided into regular and irregular. 
The regular 
ECHINI, (properly so called) Zam. C1pDaRtIs, Klein. 
Have the testa generally spheroidal, the mouth at the middle 
of their inferior face, and the anus precisely opposite. The 
little holes are ranged there on six bands approximated by 
pairs, which proceed regularly from the mouth to the anus, 
like the meridians of a globe. 
Certain species have large and thick prickles of very various 
forms, supported on thick tubercles of the testa, and the bases 
of which are surrounded with other smaller prickles. (Echinus 
mamillatus, L., &c.) 
It is among these species that are ranged, as M. de Luc 
has discovered, those whose prickles, in the form of olives, 
are frequently found petrified in chalk or other ancient forma- 
tions, and have received the name of Judaic stones. 
The most common species, and especially those of our 
coasts, have only slender spines, articulated on small tuber- 
cles, much more numerous. Such is 
Ecuinus Escuxentus, L., Klein., Lesk., I. A. B,, 
Encye. 132. 
Of the form and size of an apple, all covered with short, 
striped tubercles, usually of a violet colour. Its ovaries are 
eaten in spring uncooked, they are reddish, and of a flavour 
sufficiently agreeable. 
The neighbouring species are difficult enough to dis- 
tinguish, being marked by the greater or less approximation 
of the bands of holes, by the equality or inequality of the 
tubercles, &c. (Heh. miliaris, Kl., &c. &c. &c.) 
