MONOGRAPH OF THE LEUCOSIAM. 305 



Phlyxia l^evis, mihi (Tab. XXXIV. fig. 3). Brachiis triedris; testa laevi, margine 



laterali unidentato. 

 Hab. ad Novam Zealandiam. Mus. Brit. 



Carapace rhomboidal, smooth, rostrum obtuse, slightly emarginate ; margin of the 

 branchial region with a single minute tooth, posterior margin with three obtuse teeth ; 

 anterior legs not twice as long as the carapace ; arm three-sided, triangular, granulated ; 

 hand half the length of the arm, smooth, slightly carinated on the outer side, fingers 

 hardly deflexed. 



Length of carapace 04 in. 



The generic characters are much less strongly marked in this species than in either of 

 the others, but the form of the foot-jaws, the three teeth on the posterior margin of the 

 carapace, its rhomboidal form and other points of structure, sufficiently show its close 

 relation to them. It may be considered perhaps as osculant between this genus and 

 Ebalia. 



Genus Lithadia, Bell. 



Testa rhomboidea, rudis, regionibus gibbosis, rostro bifido, resupinato terminata. Orbita supra et extror- 

 sum aperta. Fossa antennariai obliquse. Pedipalpi externi caule exteriore ensiformi, antice obtuso ; 

 interiore lanceolate, exteriore longiore. Pedes antici robusti, rudes; brachiis tuberculatis, ad 

 marginem exteriorem cristatis; manibus cristatis, digitis approximatis. Abdomen Maris segmentis 

 tertio, quarto et quinto coalitis; Fcemin^e ? 



The grounds upon which I have thought it necessary to assign a distinct generic rank 

 to the species to which the above characters belong, closely allied as it is to Ebalia, are 

 the extremely different general aspect of the whole animal, arising from the rough and 

 strong prominence of the different regions, the projecting spines, the large and prominent 

 granulations, so unlike any other form in this family, excepting Oreophorus, and some 

 distinct though not very striking differences in the form of the external foot-jaws, the legs, 

 and particularly the abdomen in the male. 



Species unica, Lithadia Cumin gii, mihi (Tab. XXXIII. figs. 6, 7). 

 Hab. ad oras Americae centralis (Puerto Portrero). Mus. Bell. 



Carapace very strongly marked by rude elevations, sharply circumscribing deep 

 hollows. In the younger specimen of the two in my possession, the elevations are more 

 numerous and distinct, and the sulci separating them are continuous; the difference 

 in the older specimen arising from the confluence of several of these elevations, by which 

 the sulci become merely four irregular circumscribed hollows, covered within with 

 distinct granulations*. Posterior branchial lobe forming a triangular tooth; posterior 

 lobes of the cardiac region similarly modified. Rostrum slightly turned up, emarginate. 



* This difference is so remarkable, that the specimens might be considered as of distinct species were there not other 

 instances of similar variations in the surface, either from difference of age or from some ordinary law of variety. The 

 tubercles, for example, which in the normal form of Eurynome aspera are quite separate, and are distributed very 

 equally and distinctly over the carapace, are occasionally more or less confluent, forming a few tabulated surfaces ; and 

 it has, in this state, been described by Risso as a distinct species, under the name of Eu. scutellata. I have specimens 

 exhibiting intermediate states. 



