218 CRUSTACEA. 



inhabit the bodies of various Acephala or Linneean Medusae, 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 for- 

 ceps ; the six appendages of the extremity of the tail are styliform, 

 elongated and forked or bidentated at the end ; six vesicular sacs may 

 be observed between the last feet. Several sj^ecies appear to exist, 

 but they have not been strictly and comparatively described. 



That Avhich has been taken for our type is the Cancer seden^ 

 ^arm?, Forsk., Faun. Arab., p. 95; Latr., Gener. Crust, et In- 

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

 bits 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 PJironime sentinelle, Risso, Crust., II, 3, inhabits the 

 interior of Medusae, constituting the genera Equoree and Geronie 

 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 occu- 

 pied by oblong eyes somewhat cmarglnated on the inner edge ; two 

 of the antennae, at least half as long as the body and terminated by a 

 long setaceous stem composed of several small joints *. 

 Phrosine, Risso. 



Form of the body and that of the head similar to the Hyperise, but 

 the antennae, at most, the length of the latter, composed of but few 

 and styliform joints, or terminated by a stem resembling an elongated 

 cone f . 



* Cancer monoculuides, Montag., Tians. Lin. Soc. XI, ii, 3 ; — Hyperie de Le- 

 sueur, Lat., Encyclop. Method., Atl. d'Hist. Nat., CCCXXVIII, 17, IS; Des- 

 mar. Consid., p. 258. 



N.B. Near the Hyperise should be placed the genus Themisto, Lat., carefully 

 figured and described in the Mem. de la Soc. d'Hist. Nat., tome IV. As in the 

 Hyperire, the eyes are very large and occupy the larger portion of the head ; two 

 of the antennre (the inferior), all terminated by a multi-articulated stem tapering to 

 a point, are evidently longer than the others. Tlie part there called levre inferieure, 

 is the ligula ; those which appear to form the third pair of jaws are the first of the 

 foot-jaws, and, as in the Amphipoda and Isopoda, close the mouth inferiorly under 

 the form of a lip. The four remaining foot-jaws are very short, directed forwards 

 and laid upon the mouth in such a w ay that they seem to constitute a part of it, so 

 that if we do not count them, or if wc merely consider the following locomotive and 

 much more apparent organs as feet, this animal, like the Hyperia and Phrosine, 

 appears at the first glance to have but ten feet instead of fourteen. The third pair 

 of foot-jaws is terminated by a small didactyle forceps. The same pair of feet, pro- 

 perly so called, is much longer than the others ; its penultimate joint is greatly 

 elongated, and is armed with a range of small spines forming a sort of comb. But 

 a single species is known. 



t Phros. macrophthalma, Risso, Jour, de Phys., Octob. 1822; Desmar., lb., p. 

 259 ; Cancer (jidba, Montag., Trans. Lin. Soc, XI, ii, 2. 



