152 
Tnterior antenne three-jointed, terminated by two many- 
jointed sete: external antenna squamiform, four-jointed. 
Igacus is one of four distinct genera that have been 
confounded. under the general appellation Scyitiarus. 
The order of the thighs, according to their length, is 2, 
2 4, 1, and 2. 
IBACUS PERONIE. 
TAB. CXES 
I. testa utrinque pone fissuram 5-dentata, pedipalpis exter- 
nis articulo secundo crista dentata. 
Scyllarus incisus. Peron, Mus. Hist. Nat. Galic. 
Habitat in Australasia mari. 
PERON’S IBACUS. 
Shell on each side behind the fissure with five teeth; exte- 
rior pedipalpes with their crest dentated. 
The only specimen of this species that I have seen, is 
preserved in the collection of the Jardin des Plantes, where 
it was deposited by Peron, who brought it from New Hal- 
land. 
