of some rare West Indian Crustacea. 337 



quadrata. Oculi flavescentes striati. Cauda lata, articulo 

 basilar! flavescente maculis tribus brunneis, medio bilobato. 

 Venter pedesque ferrugineo maculati, unguibus brunneis. 

 Fedes 2 postici didactyli ad basin spin4 validd bifida : an- 

 tenncB internae 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. 



Ibacus. Leach Zool. Misc. 



1. Ibacus ciliatus. 



I. nigro-flavescens purpureo varius, corpore verrucoso: verrucis 

 ciliatis, test^ utrinque ante fissuram 2-dentat4 postice 6- 

 dentatd. 



Habitat in Caribeo mari rarissimus. 



Desc. Antennae externae profunde ciliato-serratae, internae fla- 

 vescentes purpureo-lineatae : pedipalpi externi articulo pri- 

 me et secundo crista duplici dentatd. Pedes 2 postici ad 



I basin spina validA, simplici. 



Atya. 



