38 ZOOLOGY. 
around the cesophagus, with branches to the rays, &c. The mouth is armed | 
with hard bony teeth, enabling the animal to live upon erustacea and shell 
fish. Some live at the bottom of the sea on the surface of the rock, and 
others burrow in the sand. 
The integument of some of the members of this class is sustained by a 
calcareous skeleton, which incloses the viscera and supports movable spines. 
varying much in size and shape. The skeleton is composed of pieces which 
are often joined together like polygonal stones in a pavement. These 
plates, the spines, and the entire skeletons, are very abundant in various 
geological formations, in which they are preserved in great perfection. 
The class contains the orders Crinoidea, Asteridea, Echinidea, Holothuri- 
dea, to which some add another for the reception of Siponculus, Echiurus, 
&e., constituting the apodous Echinodermata of Cuvier. 
Orver 1. Crrvomea. This order is almost extinct, but is found plentifully 
in a fossil state in the older rocks. These remains consist of the solid 
calcareous skeleton, of which the chief parts are the stem, the body, and 
the arms. The body is oval or cup-shaped, protecting the internal soft 
parts, and made up of numerous plates, of which the variations in number 
and form afford generic characters. The arms are five or more in number, 
simple or branched, fringed with lateral articulated appendages, and placed 
around the upper margin of the body, the mouth being situated between 
them. When the arms are closed, some species resemble a lily, whence the 
trivial name of Ancrinus liliiformis. The vent is distinct and lateral. 
The central solid part of the stem has been compared to the bones in a 
lizard’s tail, being made up of a column of disks, which are either circular, 
polygonal, or star-shaped. The stem is often provided with articulated 
simple lateral branches, which, like the arms, are filled with calcareous 
joints, many thousand of which are contained in the remains of a single 
animal. The disks of the stem have a perforation through them, which 
admits of their being strung like beads; and, according to Dr. Buckland, 
they were used for resaries in ancient times. In northern England they are 
called St. Cuthbert’s beads ; and before their nature was known, they were 
named Entrochites in books. 
Pentacrinus asteria, Linn. (P. caputmeduse, Miller) (pl. 76, fig. 58), is 
a recent species from the West Indies, of which a specimen is in the British 
Museum, the Paris Museum, that of the Geological Society of London, and 
that of the London College of Surgeons. (This and other species of the 
order are figured in the Penny ae ix. 390, and in the new edition of the 
Régne aca) Encrinus radiatus (fig. 57 ). 
Pentacrinus europeus, Thompson, a minute animal found on the coast of 
Ireland, is now considered by this author to be the pedunculated young of 
Comatula, a starfish somewhat like pl. 76, jig. 62. This confirms one of 
the views of Agassiz (Lectures, p. 13), that the earlier fossil animals often 
resemble the embryonic or immature forms of the more recent periods. 
Holopus rangi, Orbigny (pl. 76, fig. 56) (Mag. de Zool. 1837, pl. 3) is a 
recent genus from Martinique. 
Orver 2. AstertpEs. In this order the supporting stem is wanting, and 
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