PEDICELLATA. 395 



of their shell, and then to remove it. The mouth is provided with 

 five teeth, set in an extremely complex, calcareous framework, resem- 

 bling- a pentagonal lantern, furnished with various muscles, and sus- 

 pended in a large aperture of the shell. These teeth, which resem- 

 ble long ribands, become indented inferiorly as fast as they are worn 

 away at the point *. The intestine is very long, and attached, spi- 

 rally, to the interior parictes of the shell by a mesentery. A double 

 vascular system extends along this canal, and partly on the mesen- 

 tery ; there are also particular vessels for the feet. Five ovaries, 

 situated round the anus, empty themselves by separate orifices; they 

 form the edible portion of these animals. 



The Echini chiefly feed on small shell-fish, which they seize with 

 their feet. Their motions are very slow. Shells of Echini are very 

 abundant in the ancient strata, principally those of chalk, where they 

 are usually filled with silex. 



The Echini should be divided into regular and irregular. 



In the first. 



Echinus, Lam. - Sidaris, Klein., 

 Or Echinus properly so called, the shell is generally spheroidal, the 

 mouth in the middle of the inferior surface, and the anus diametri- 

 cally opposite. The little foramina are arranged in ten bands, ap- 

 proximated by pairs, that extend regularly from the mouth to the 

 anus, like the meridian lines of a globe. 



Certain species are furnished with large and stout spines of vari- 

 ous forms, placed en large tubercles on their shell, the bases of 

 which are surrounded by other but smaller spines f. 



It is among these species, as ascertained by M. Deluc, that we 

 must place those whose olive-like spines are often foimd petrified in 

 chalk, and other ancient formations, called pierres judaiques X. 



The most common species, and particularly those of the coast of 

 France, are merely furnished with slender spines, articulated on 

 small tubercles that are much the most numerous. Such is the 



E. Odcidentus, L. ; Klein., Lesk., I, A, B; Encyc. 132. The 

 common Echinus is of the form and size of an apple, completely 

 covered with short, radiating, and usually violet spines. Its 

 ovaries, which are reddish, and of anagreeable flavour, are 

 edible in the spring. 



The neighbouring species arc distinguished with difficulty, by the 



* See my Le9ons d'Anat. Comp., IV, and the work of Tiedemann, already 

 quoted. 



f Echintis mammillatus, L.; Seb., Ill, xiii, 1 — 4; Encyc, pi. 138, 139, aad the 

 naked shell, lb., 138, 3, 4. — The different species approximated under the name of 

 Erh. Sidaris, Scill., Corp. Mar. Tab., xxii; Seb., Ill, xiii, 8, &c. ; — Ech. verticillafus. 

 Lam.; Encyc., 136, 2, 3 ; — Ech. tribulo'idcs, Id. Encyc, lb., 4, 5 ; — Ech. jnstillaris. 

 Id., Encyc, 137 ; — Ech. stellatus, L. ; Seb., Ill, xiii, 7 ; — Ech. araneifonnis, Id., lb., 

 G; — Ech.saxatilis, Id., lb., 10; — Ech. calamarius, Pall.; Spicil. Zool., X, ii, 1 — 7. 



I See tlie Letters from Switzerland of Andreis, pi. XV, and the Memoir of M. 

 Deluc, M(im. des Sav. Etrang., IV, 467. 



N. B. The naked shells are distinguished with difficulty; such are the Ech. exca- 

 rafus, L. ; Scill., Corp. Mar., xxii, 2, D; — Ech. ovarius, Bourguet., Petrif., LII, 

 344, 347, .348. 



1)» 2 



