60 CRUSTACEA. 



separates them from the fourth or that of the Carides. The an- 

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

 the lateral ones, when accompanied by a scale, is never entirely co- 

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

 feet. The two mediate antennae are always terminated by two fila- 

 ments only, usually shorter than their peduncle, or scarcely any 

 longer. The external leaflet of the natatory appendages of the pe- 

 nultimate segment of the tail is never divided by a transverse suture. 

 In our second section, or the Locustje, so called from the name 

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

 division, and from which is derived that of Langouste applied to 

 them in France, there are never more than four 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 antennae is always longer than the two terminal fila- 

 ments, and more or less bent or geniculate; the lateral ones are 

 never furnished 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 and long, terminating in a point and bris- 

 tled with spines. All the feet are nearly similar and end in a point; 

 the two first are merely somewhat larger; their penultimate joint and 

 that of the two last are at most unidentated, but without forming 

 with the last a perfectly didactyle hand. The pectoral space in- 

 cluded between the feet is triangular; the thorax is almost square or 

 sub-cylindrical, and without any frontal prolongation or rostrum. 



Scyllarus, Fab. 



The Scyllari, or Sea-Grasshoppers as they are called, present a 

 very unusual character in the form of their lateral antennae; the stem 

 is wanting and the joints of the peduncle, very much dilated trans- 

 versely, form a large, flattened, horizontal crest more or less den- 

 dated. 



The external branch of the sub-caudal appendages is terminated 

 by a leaflet; but the internal one, in some of the males, is a mere 

 tooth. 



Doctor Leach has established three genera of them, founded on 

 the proportions and form of the thorax, the position of the eyes, and 

 some other parts. They are, 



1. Scyllarus, where the thorax is as long as it is broad or longer, 

 and without any lateral incisure, the eyes always situated near its ante- 

 rior angles; the penultimate joint of the two posterior feet uniden- 

 tated in the females. They excavate holes in the clayey soil near 

 the shore which serve them for habitations. 



