381 



Maxillipeds nearly of same structure as in the genus Acanthonotosoma, though 

 having the masticatory lobes comparatively larger. Gnathopoda very unequal, 

 the anterior ones being extremely slender, and terminating with a minute chela, 

 whereas the posterior ones are rather robust and subcheliform, the propodos 

 being considerably expanded, and having a distinctly defined palm. Pereio- 

 poda very strongly built and nearly of equal length, basal joint of the 3 

 posterior pairs laminarly expanded. Last pair of uropoda with the rami very 

 unequal in length. Telson oblong, minutely incised at the tip. 



Eemarks. - - This genus was established by Sp. Bate as early as in 

 the year 1802, but as the generic name he proposed was already appropriated 

 in Ornithology, Lilljeborg changed it to Odius. The genus, though evidently 

 belonging to the same family, is well defined from the 2 preceding ones, both 

 by the external appearance and by several structural details, especially as 

 regards the oral parts and the posterior gnathopoda, The genus comprises 

 as yet but a single species, to be described in the sequel. 



5. Odius carinatus, (Sp. Bate). 



(PI. 133, fig. 2). 

 Otus carinatus, Sp. Bate. Catal. of Amphip. in the British Mus., p. 126, PL XXIII, fig. 2. 



Body very short and stout, highly compressed, and distinctly cari- 

 nated throughout the whole mesosome and metasome, the carina, however, 

 not being elevated to dorsal projections, except on the 2 last segments, 

 anterior projection obtusely rounded, posterior acute and erect. Cephalon 

 comparatively short, rostrum acute and perpendicularly deflexed, reaching 

 considerably beyond the basal joint of the superior antennae, lateral corners 

 forming, on each side, a rather large triangular lobe. First pair of coxal 

 plates tapering to an obtuse point ; the 2 succeeding pairs narrowly trun- 

 cated at the tip; 4th pair rather large, with the anterior edge nearly 

 straight, and the posterior projection rather produced and acuminate; the 2 

 succeeding pairs having the posterior lobe truncated at the tip. Last pair 

 of epimeral plates of metasome biangular at the lateral corners, inferior angle 

 but little produced, superior one jutting out as a recurved acute projection 

 defined above by a deep sinus. Eyes of moderate size, reniform, pigment 

 red. Superior antennae scarcely attaining the length of the cephalon and 

 the 1st segment of mesosome combined, 1st joint of the peduncle simple, 

 and about as long as the other 2 combined, flagellum much shorter 

 than the peduncle, and composed of 7 articulations only, the outer 3 of 

 which are very small and clothed with long sensory filaments. Inferior 

 antennae still shorter than the superior, with the flagellum extremely 



49 Crustacea. 



