DECAPODA. 195 



fectly didactyle hand. The pectoral space inchided between the feet 

 is triangular ; the thorax is almost square or sub-cylindrical, and with- 

 out any frontal prolongation or rostrum. 



SCYLLARUS, Fab. 



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

 usual 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 tliorax, the position of the eyes, and 

 some other parts. They are, 



1. ScYLLARUs, where the thorax is as long as it is l)road or longer, 

 and without any laternal incisure, the eyes always situated near its 

 anterior angles ; the penultimate joint of the two posterior feet uni- 

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

 the shore, which serve them for habitations. 



In one of them the Scyllare ours ; Cancer arclua, L. ; Cigale 

 de mer. Rondel., liv. XIII,chap, VI; Herbst,, XXX, 6,the external 

 or lateral antennae are much dentated. The thorax is marked with 

 three longitudinal and dentated ridges, and the superior surface 

 of the tail sculptured, but its lateral margin not crenulated. 



The other, Sci/llarus (equinoxialis, Fab.; Scyllarus orientalis, 

 Risso; Squille large, or the Orc/ietta, Rondel. ; Gesn., Hist, des 

 Anim., Ill, p. 1097, is large, shagreened, and without ridges. 

 The crests are edentated, and the margin of the segments of the 

 tail crenulated. Its flesh is highly esteemed, and the ova are of 

 a vivid red. 



2. Thenus, where the fore part of tlie thorax is broader than it is 

 long, each lateral margin deeply incised, and the eyes are placed at 

 its anterior angles*. 



3. Ibacus, only differing from Thenus in the position of the ej^es, 

 which are approximated to the origin of the intermediate antennae. 



In an Australian species, Ibacus Pronii, Leach, Zool. Miscel., 

 CXIX; Desmar., Consid., XXX, 12, the exterior lateral margin 

 of the third joint of the external foot-jaws is transversely striated, 

 and notched in the manner of a crest f. In the 



* Themis intUcus, Leach; Sci/Uarus orientalis, Fab.; Rumph,, Mus., II, D. ; 

 Herbst., XXX, 1 ; Encyc, Atl. d'Hist. Nat., CCCXIV ; Desmar., Consid., 

 XXXI, 1. 



t Add Scyllarus antarcticus ; Fabr., Herbst., xxx, 2 ; Rumph, , Mus., II, D. See 

 the article Scyllare, Encyc. Methodique. 



o2 



