SYSTEMATIC 

 ARRANGEMENT OF ECHINODERMS. 



CLASS IV. 

 ECHINODERMATA. 



ANIMALS with integument coriaceous, often calcareous; with 

 distinct nutrient canal, freely suspended in an abdominal cavity. 

 Organs of circulation and generation conspicuous ; sexes nearly 

 always distinct. Disposition of the organs most frequently quinary, 

 with body mostly radiate or globose, in some cylindrical. Distinct 

 vestiges of a nervous system, a ring for the most part surrounding 

 the mouth and sending off nerves radially. 



OEDER I. Pediculate Echinoderms. 



Tentacles numerous, membraneous, contractile, terminated by a 

 suctorial disc, and issuing from minute apertures in the integument. 



Family I. Crino'idea. Integument calcareous (external skele- 

 ton). Rays articulate, supplied with a central canal, absent in 

 some. Mostly two apertures of the nutrient canal. 



The name Crindidea, given by MILLEK to this division of the ani- 

 mal kingdom, is derived from Kpivov, a lily. At the beginning of the 

 last century the name sea-lily, stone-lily was given to the Encrinus 

 moniUformis, or liliiformis, a remarkable petrifaction of the Muschel- 

 kalk. Most of them are set upon a stem ; the non-pediculate (Coma- 

 tula LAM.) in the young state, according to the observations of 

 THOMPSON, are also fixed to a pedicle. The non-pediculate species 

 known to LINNAEUS were placed by him in the genus Asterias (Aste- 

 rias pectinata, Ast. multiradiata) ; the pediculate species in the 



