818 Mr. G. R. Waterhouse on some new genera and 



rounded ; the lateral keel is very distinct^ acute, and remote 

 from tlie lateral margins of the elytra. 

 Legs moderate ; the anterior tibise but little compressed, and very 

 little dilated at the extremity : they are provided with a short 

 spine on the inner side at the apex, and the outer angle is 

 somewhat prominent. Tarsi moderate as to thickness and 

 rather long, those of the middle and hind legs being equal to 

 the tibise in length, and those of the anterior pair of legs but 

 little shorter than the tibise from which they spring : claws 

 rather large. 

 Praste7num not produced posteriorly. 



This genus, to which I have given the name Platesthes in allu- 

 lusion to its flat covering, the whole back of the insect being de- 

 pressed and nearly on the same plane, evidently approaches closely 

 to the genera Gyriosomus and Praocis, near to which should also 

 be placed, in my opinion, the genus Physogaster. The last-men- 

 tioned genus, M. Le Comte de Castelnau says, is closely allied to 

 Pimelia ; but in making this assertion he must entirely have over- 

 looked the structure and position of the labium, a part of the 

 mouth which furnishes good characters for the sections of the 

 Heteromera. On this subject I cannot enter at present, but I 

 will merely remark, that in the Pimelidce, Akisidce, TentyriidcB and 

 Erodiidcs the labium is attached to the back part of the mentum 

 in such a manner as to be totally hidden, or, at most, to leave ex- 

 posed the points only of the paraglossse * ; to these we may also 

 add the Adesmia anAEpiiragus group f. In the genus, the affi- 

 nities of which T wish to determine, as well as the genera with 

 which I have associated it, the labium is attached to the anterior 

 extremity of the mentum, and is completely exposed and com- 

 bined with a great similarity in the structure of other parts of 

 the mouth ; they all have the throat-plate marked with the pecu- 



* The term paraglossae is applied by Kirby and Spence to the lateral lobes 

 of the labiuni of the bees, and as the same parts exist in beetles, I think it 

 well to call them by the same name ; they lie for the most part behind the 

 tongue, and are nearly always fringed with hairs in the Heteromera ; but in 

 the latter groups (according to Dejean's arrangement of the order), Taxi- 

 comes and Tenebrionites, where the tongue is narrower, the outer margins 

 of the par^glossse are distinctly exposed ; in some cases where the tongue is 

 broad, as in BoUtophagus, the paraglossse are still very distinct (viewing the 

 labiupi from its outer surface), projecting as they do considerably iu the 

 lateral direction. 



f Why should not these groups, in which the tongue is hidden, be asso- 

 ciated together? We might commence with Epitragus, and continue 

 through the other groups, Tentyriidce, Erodlidce, Adesmia, he. y where there 

 is no separate emargination for the maxillee, and where the mentum covers 

 that organ, to the f^melidce, Ak'mdce and Nycfelidce, where there is a sepa- 

 rate notch in t^^e. tihrft^t-pUto far t\\^ maxillae, which are exposed — at the base 

 at least. 



