162 CLASS CRUSTACEA. 



The species whose testa is transverse, with the middle of 

 the sides greatly prolonged, or dilated in the manner of a 

 cylinder, or cone, form his genus Ixa, [Leucosia cylmdrus, 

 Fab.) 



Those whose testa is rhomboidal, with seven conical 

 points, in the form of spines, on each side, compose that of 

 IpJiis. 



If the testa, having always the same rhomboidal form, 

 presents only angles or sinuses on the sides, we shall have his 

 genus Nnrsia ; and that of Ehalia, if these lateral edges 

 are smooth. 



The leucosise, with ovoid, or almost globular testa, and dis- 

 tinguished besides from many of the preceding, by having the 

 claws always longer than the body, and thicker than the other 

 feet, and the tarsi sensibly striated, may be thus divided. 



Some have the point advanced beyond, or at least not out- 

 edged by the superior extremity of the buccal cavity. The 

 external branch of the exterior jaw-feet is elongated, and 

 almost linear. In these the claws are slender, with the hands 

 cylindrical, and the fingers long. 



Sometimes the testa is almost globular, and either very 

 spiny, as the genus arcania, or even as in that of ilia. 



Sometimes the testa is suborbicular and depressed, as in 

 the genus persephona ; or it is ovo'id, as in that of myra. 



In some the claws are thick, with the hands ovo'id, and short 

 fingers. These are the true Leucosice of this naturalist. 



In the others, the superior extremity of the buccal cavity 

 passes the front or forehead. The external branch of the ex- 

 terior jaw-feet is short and arched; the testa is rounded and 

 depressed. 



This last division comprehends his genus phylira. 



Other considerations, taken fi'om the proportions of the feet, 

 and the form of the external jaw-feet, support these characters. 

 Ilia nucleus, Leach. 



12 



