LEUCOSIADiE. 
23 
Genus 16. IXA, 
Chau. Gen. —Testa elliptico-rhomboidalis, processu utrinque 
subevlindrico a regione branchiali produeto ; regionibus sulco 
profundo separatis. Orbita supra bifissa. Fedipalpi externi 
caule exteriore lato, obtuso, interiore longiore. Pedes omnes 
filiformes, tenues. Abdomen Foemince articulo ultimo usque 
ad oris aperturam produeto. 
Ixa, Leach, Trans. Linn. Soc. xi. p. 334. 
Edw. Hist. Nat. Crust, ii. p. 134. 
1. Ixa cylindrus. B.M. 
Cancer Cylindrus, Fabr. Mantissa , 251. 
Herbst, i. p. 108. t. 2. f. 29, 30, 31. 
Leucosia Cylindrus, Fabr. Suppl. 352. 
Latr. Hist. Nat. Crust, vi. p. 119. 
Licht. Berl. Mag. 1815, p. 143. 
Ixa Cylindrus, Leach , Trans. Linn. Soc. xi. p. 334. 
Bell, Trans. Linn. Soc. xxi. p. 311. 
Ixa canaliculata, Leach, Zool. Misc. iii. p. 26. t. 129. f. 1. 
Edw. Reg. Anim. Cuv., Crust, t. 24. f. 1; id. Hist. Nat. 
Crust, ii. p. 135. 
Ixa megaspis, Adams fy White , Voyage of the Samarang, Crust . 
p. 55. t. 12. f. 1. 
(Senior.) B.M. 
Ixa inermis, Leach, Zool. Misc. iii. 1.129. f. 2. 
Edw. Hist. Nat. Crust, ii. p. 135. 
Hab. In mari Indico. 
Obs. A careful examination of all the specimens of this genus 
to which I have access, amounting to about twelve, has led me 
to conclude that the}^ all belong to one species. The variations 
which exist between any two of them are nearly as great as those 
which have given rise to the establishment of a distinct specific 
name in the case of I. megaspis of Messrs. Adams and White. 
I possess two specimens which were obtained by Mr. Hinds, 
which differ so much from others, that until I had carefully exa¬ 
mined the whole of those I have alluded to, I had provisionally 
given them a distinct specific name. The form and size of the 
lateral process vary considerably. In some it is cylindrical, in 
others it is somewhat conical; in some it is either direct or even 
bent slightly backwards, in others the apex is turned forward; 
in some there is a filiform appendage at its apex, in others there 
