Ig4 CRUSTACEA. 



which are strongly svilcated with longitudinal ridges. The right 

 one is the largest *. 

 A fourth from the same sea is removed from the preceding by 

 several characters, and merits the distinction of forming a separate 

 subgenus, the Prophylax, Latr. Tlie tail, with the exception of the 

 superior surface of the three last segments, instead of being soft 

 and arcviated, and having but a single range of oviferous filaments, is 

 covered with a coriaceous tegument, is straight, and is only curved 

 beneath at its extremity ; its inferior surface presents a groove and 

 two rows of false feet. The body also is linear, and the two lateral 

 appendages of the end of the tail are almost equal, the larger divi- 

 sion being foliaceous and ciliated. The last four feet are slightly 

 granulated at their extremity, and appear to be terminated by a sin- 

 gle finger, or at least arc not distinctly bifid. Perliaps we should 

 rc-fer to this division those Paguri which inhabit the Serpixla?, and 

 Alcyonii, s\ich as the Parjurus tubularius. Fab. 



In all the following Macroura, the two posterior feet at most are 

 smaller than the preceding ones. Most generally the sub-caudal 

 false feet form five pairs. The teguments are always crustaceous. 

 The lateral fins of the penultimate segment of the tail, and its last, 

 form a common one arranged like a fan. 



The two subsequent sections possess a common character, which 

 separates them from the fourth or that of the Carides. The antenna' 

 are inserted at the same height, or on a level ; the peduncle of the 

 lateral ones, when accompanied by a scale, is never entirely coA'ered 

 by it. There are frequently but four pairs of sub-caudal false feet. 

 The two mediate antenna- are always terminated liy two filaments 

 onlv, visually shorter than their peduncle, or scarcely any longer. 

 The external leaflet of the natatory appendages of the penultimate 

 segment of tlie tail is never divided by transverse suture. 



In our second section, or the Locusta;, so called from the name 

 Locusta given by the Latins to the most remarkable Crustacea, of 

 this division, and from Avhich is derived that of Langouste, applied to 

 them in France, there arc never more than fovir pairs of false feet. 

 The posterior extremity of the fin that terminates the tail is always 

 nearly membranous, or less solid than the rest. The peduncle of 

 the mediate antennjie is always longer than the two terminal filaments, 

 and more or less bent or geniculate ; the lateral ones are never fur- 

 nished with scales ; sometimes they are reduced to a single peduncle 

 which is dilated, very flat, and in the form of a crest ; sometimes they 

 are large ajid long, terminating in a point and bristled with spines. 

 All the feet are nearly similar and end in a point ; the two first are 

 merely somewhat larger ; their i)enultimate joint and that of the two 

 last are at most unidentated, but without forming with the last a per- 



* For the other species see the article Pagitre, Encyc. Method. ; the Atlas 

 d'Hist. Nat., of the same work; Desmarest, Consid('T. Gener. sur la Classe des 

 Crust. ; the plates of tlie Voy. de Freycinet. We should observe that in the figure 

 of the Cancer mecjistos, Herbst., LXI, 1, the tail is false; this arises from the fact 

 that the tail was wanting in the individual from which the drawing was made, the 

 artist supplying it by copying the fin-tail of an ordinary Macroura. 



