394 ECHINODERMATA. 



But one very small species — Penlacrinus europceus, Thorns., 

 Afonog'. — is found in the seas of Europe ; it attaches itself to va- 

 rious Lithophyta. 



The seas of hot climates produce larger and more complicated 

 ones, such as the Encr. asteria^, Blum.; Isis aster, L. 



Fossil Encrinites however are very numerous, and so various, that 

 they have been divided into several sid)genera, according to the com- 

 position of the central body placed on the summit of the stem, and 

 from which the large rays proceed. 



This body may be formed of pieces articulated with the stem, and 

 bearing the rays by similar arlijulations. In this case, and if the stem 

 be round and inflated above, we have the Apiocrinites, iMiller; 



If it be round, but not iiiMated, Encrinites ; 



If pentagonal, Pentacrtnus. 



Or tliis body may be formed of angular plates united at the edges, 

 and forming several ranges. Of these 



The Platycrintes have but two ranges one of three plates, tlii> 

 other of five ; 



The Poteriocrinites have three ranges, each consisting of five 

 plates; 



The Cyathocrinites also three, and each of five, but the last is 

 furnished with intercalated plates which may increase it to ten ; 



The AcTiNOCRixiTES have several ranges, the first of three, the 

 second of five, and the others more numerous. The two first are 

 marked with radiating ridges ; 



The Rhouocrinites also have several ranges, the first of three, 

 the second of five, and third of ten, all the three with ridges; the 

 others are more numerous. 



Finally, the central body may be formed of one piece, which ap- 

 pears, however, to consist of five pieces soldered together : here we 

 have the Eugeniacrinites *. 



The fossil productions, known by the names of Entrochites, are 

 portions of the stem and branches of animals belonging to this genus. 



Echinus, Lin. 



The Echini, or Sea-Urchins, as they are termed, have the body in- 

 vested by a shell or calcareous crust, composed of angular pieces 

 which join each other exactly, and perforated by innumerable holes, 

 for the transmission of the membranous feet, disposed in several 

 very regular ranges. The surface of this crust is armed with spines, 

 articulated on little tubercles, that move at the will of the animal, 

 whose motions, conjointly with the feet situated between them, they 

 effect. Other membranous tubes, much finer and frequently divided 

 at the extremity, probably serve to convey water into the interior 



* No one has so carefully studied these productions, or described them so exactly 

 as M. J. Miller, iu his Nat. Hist, vf the Crinuidea, Bristol, 1821, in 4to. It is to 

 this work that we are indebted for our article. Excellent figures of the same are 

 also given bv M. Georsre Cumberland, in his Relitjuice Conservata, Bristol, 1826. 



