88 CRUSTACEA. 



1. Those which have fourteen feet all terminated by a hook, or in 

 a point. 



2. Those which also have fourteen feet, but which are — the four 

 last at least — simply natatory. 



3. Those which have only ten apparent feet. 

 The first section is divided into two. 



Some of them, — the Uropteua, Latr., usually have a large head; 

 the antennae are frequently short, and in some but two in number; 

 the body is soft. All the feet, the fifth pair at most excepted, are 

 simple, the anterior are short or small, and the tail is either fur- 

 nished at the extremity with lateral fins, or is terminated by points 

 or appendages, widened and bidentated, or forked at their posterior 

 extremity. They inhabit the bodies of various Acephala or Lin- 

 naean Medusse, and of some other Zoophytes. 



Here, as in 



Phronima, Lat., 



There are but two — very short and biarticulated — antennae; the 

 fifth pair of feet is the largest of all and terminates in a didactyle 

 forceps; the six appendages of the extremity of the tail are styli- 

 form, elongated and forked , or bidentated at the end; six vesicu- 

 lar sacs may be observed between the last feet. Several species ap- 

 pear to exist, but they have not been strictly and comparatively de- 

 scribed. 



That which has been taken for our type is the Cancer seden- 

 tarius, Forsk. , Faun. Arab., p. 95; Latr., Gener. Crust, et In- 

 sect. I, ii, 2,3, which is found in the Mediterranean, and in- 

 habits a membranous transparent body that has the figure of a 

 cask, and which appears to proceed from the body of a species 

 of Beroe. 



The Phronime sentinelle, Risso, Crust., II, 3, inhabits the in- 

 terior of Med usee, constituting the genera Equoree and Ge'ro- 

 nie of Peron and Lesueur. Another species, according to Leach, 

 has been observed on the coast of Zealand. 

 There we observe four antennae; all the feet are simple; on each 

 side of the extremity of the tail is a lamellated or foliaceous fin, the 

 leaflets of which are acuminated or unidentated at the end. 



Hyperia, Lat. 



The body thickest anteriorly; the greater portion of the head oc- 

 cupied by oblong eyes somewhat emarginated on the inner edge; 



