Cos piiiLosornv of zoologV. 



Class I. EcniNODERMATA. 



Skin coriaceous or criistaceous. Intestinal canal distinct^ 

 and contained in an abdomen. Numerous vessels likewise 

 appear connected with circulation and reproduction. 



Order I. — Intestine open at both extremities. 



Section 1. Furnished with suckers for locomotion. 



The coriaceous skin is pierced by numerous pores, through 

 which issue tubular tentacula, connected centrally with a vas- 

 cular system, and furnished with terminal suckers. There 

 are three tribes, two of which are formed from tht Linneart 

 genera Echinus and Holothuria. 



1st Tribe Echinida. 



The integument consists of an immoveable testaceous 

 perforated plate. The body is orbicular or depressed, and 

 not divided into arms. The mouth is seated in the under 

 surface. The intestine terminates in an anus. Lamark 

 distributes the genera in the following order : 



A. Anus in the margin, or inferior disc. 



1. Mouth central. 



a. Avenues of poi'es circumscribed, as Scutella, Clypeas- 

 ter and Fibularia. 



b. Avenues of pores complete, as Echinoneus and Gale- 

 rites. 



2. Mouth lateral, as Ananchytes and Spatangus, 



B. Anus in the upper disc. 



(1.) Anus lateral, as Cassidulus and Nucleolites, 

 (2.) Anus vertical, as Echinus * and Cidarites. 



• The species of the genus Pedicellaria, instituted by Muller, and 

 adopted by many naturalists, are, in fact, the appendages of the Echinus. 

 The late Dr Mokro stated, that, " in the interstices of the thorns, there are 

 three kinds of bodies, soft at the ends, supported on calcareous stalks, en- 



