of some rare West Indian Crustacea. 337 
quadrata. Oculi flavescentes striati. Cauda lata, articulo 
basilari flavescente maculis tribus brunneis, medio bilobato. 
Venter pedesque ferrugineo maculati, unguibus brunneis. 
Pedes 2 postici didactyli ad basin spina valida bifida: an- 
tenné interne purpurascentes. 
The species of this genus are involved in great confusion from 
the imperfect and concise descriptions of naturalists. I have 
thought proper, therefore, to lay down the specific characters of 
the last-mentioned crab from a living specimen. It was formerly 
confounded with S. arctus, from which Fabricius in his Supple- 
ment very properly separated it. The figure of Browne is tole- 
rably correct, but being taken from a male specimen, the two 
posterior feet are represented as simple. On the basilar segment 
of the tail beneath are two oblong approximate shelly plates, the 
use of which is unknown. 
Igacus. Leach Zool. Misc. 
— 1. Ibacus ciliatus. 
I. nigro-flavescens purpureo varius, corpore verrucoso: verrucis 
ciliatis, testa utrinque ante fissuram 2-dentatá postice 6- 
dentata. 
Habitat in Caribeo mari rarissimus. 
Desc. Antenne externe profunde ciliato-serratæ, interne fla- 
vescentes purpureo-lineatæ : pedipalpi externi articulo pri- 
mo et secundo cristá duplici dentaté. Pedes 2 postici ad 
basin spina valida simplici. 
ATYA. 
