RADIATA. 609 



2d Tribe, Fistulida. 



This tribe resembles the preceding in the intestine being 

 open at both extremities, but the skin is coriaceous and 

 moveable. The body is lengthened, and the head is sur- 

 rounded with tentacula, and furnished with a circle of os- 

 seous pieces, as teeth. Gills arborescent near the anus. Ova- 

 rium, consisting of multifid vesicles opening by a common 

 oviduct near the mouth. The genus Holothuria, of which 

 this tribe consists, may, with propriety, be subdivided into 

 several genera. 



Section 2. Destitute of suckers for locomotion. 



This section includes the following genera, the relations of 

 which with one another are not very intimate : Molpadia, 

 Menyas, and Sipunculus. 



Order II. 



Intestine open at the mouth only. No anus. 



1st Tribe, Stellerida. 



Suckers for locomotion. The integuments are moveable, 

 and the depressed body is divided into angles or arms. The 

 mouth is inferior. The stomach is a central bag. Traces 

 of a nervous system have been discovered. There are four 

 genera, Asterias, Opliiura, Euryale, and Comatula. 



2d Tribe, Crinoidea. 



No suckers for locomotion. Body, opposite the mouth, 

 produced into an articulated stalk, the extremity of which 

 is probably fixed to other bodies. Only one recent species, 

 Pentacrinus caput Medusae *, is known ; but the characters 



closed in a membrane, and articulated with the shell by means of muscular 

 membranes." — Struct, and Phys. of Fishes, p. 66. I lately had an oppor- 

 tunity of satisfying myself that these organs in the E. esculentus are in or- 

 ganical connection, and consequently that the genus Pedicellaria is a spurious 

 one. 



• Phil. Trans. 1761, T. xiii. xiv. 



VOL. II. ft q 



