622 Mr. J. O, Westwood on the Taussidce, 



. mis (priori paul6 raajori, globoso) ; ultimo magno, long^ 

 ovato, aut cylindrico-subulato, apice acuto. Thorax sub- 

 cylindricus, paul6 longior quam latior, antice plerumque 

 dilatatus, parte elevata anticA, plCis minilsve articuliformi. 

 Elytra postic^ truncata. 



The characters given above will at once separate the species 

 of the genus from their immediate affinities, the palpi mate- 

 rially assisting in tracing the boundaries of the genus. 



It will be observed that Afzelius (who, notwithstanding his 

 admitted inability satisfactorily to examine the trophi of the 

 genus, has given their characters drawn from an external com- 

 parison of P. microcephalus and sphcerocerics,) has, as might have 

 been expected, fallen into several errors, chiefly regarding the 

 nomenclature of the different parts : — thus his polpi inleriores are 

 the labial palpi ; his palpi exteriores, the anterior produced lateral 

 lobes of the mentum; his mandibulcB, the maxillary palpi ; his* max- 

 illcB are i\\e mandibles ; and his gula triangularis is the mentum. 



This author, however, most properly considered the flat plate- 

 like part which closes the underside of the mouth, as the lower 

 lip (labium) ; and (with the exception of the anterior lateral lobes 

 of the mentum being incorrectly articulated, to represent palpi, 

 as they were considered ; and the maxillary palpi being repre- 

 sented as without joints, being regarded as the mandibles,) his 

 figures of the underside of the heads of both species correctly 

 exhibit the general structure of the various parts of the mouth 

 as seen externally. 



Latreille, however, both in the Histoire Nalurelle and Genera 

 Crustaceorum, SfC. appears to have regarded the organs, which 

 Afzelius described as the external palpi, and which I have de- 



* It must be borne in mind that Afzelius is not blameable for this variation of 

 nomenclature, since it was in accordance with that of Fabricius, adopted by liim,— 

 See Kirby and Spence, vol. iii. p. 429. 



scribed 



