RADIATA. 611 



cies of which have been described by LAMOUROUX, in his 

 " Memoire sur la Lucernaire campamdee *." 



Order II. 



Base opposite the mouth incapable of adhering to other 

 bodies. This includes the numerous kinds of Medusae 

 which float about in the water. 



1st Tribe. 



Body floating in the water, without air-bags. 



A. Body closed opposite the mouth. 



1. Body strengthened internally by a cartilaginous plate. 

 This includes the genera Velella and Porpita -f-. 



2. Body destitute of an internal cartilaginous plate. The 

 numerous genera of this group have been arranged with 

 considerable care by PERON and LESEUR, in their valuable 

 paper in Annales du Museum, vol. xiv. p. 325. Many cha- 

 racters are employed, which it may be proper here to notice. 

 Some of the species have neither mouth nor cavity, and are 

 termed Agastrique ; while others possess both. Some have 

 a mouth and stomach, without lateral openings ; while, in 

 others, the lateral openings exist, and were considered as 

 mouths by the authors just cited ; while CUVIER now re- 

 gards them as the orifices of the oviducts. In some, the 

 mouth is produced into proboscis, either simple at the ex- 

 tremity, or divided into fringed lips. In others the mouth 

 is sessile. In some, the margin of the body is simple. In 

 others, fringed with tentacula. The body, in some, is 

 smooth ; in others, covered with ridges of fine hairs, which 

 are used as fins. 



B. Body open at both extremities. This includes the 

 animals arranged under the genus Beroe. This genus ap- 



* The Hydra glomerata, Lin. Am, Acad. iv. T. iii. f. 1. may probably 

 be included in this genus. 



f- Two species of Velella, and one of Porpita, are described by Dr LEACH, 

 in TUCKEY'S Narrative, p, 418. 



(iq 2 



