724 NOTES ON AUSTRALIAN COLEOPTERA, 



lobes of the mentum are pointed at the apex, while in the latter 

 the lobes of the mentum are rounded at the apex. Both genera 

 were founded by Dejean for African species, some American insects 

 having been doubtfully attributed afterwards to Drhnostoma and 

 some from the European coasts of the Mediterranean having been 

 attributed to Ahacetus. M. de Chaudoir expresses doubt as to 

 Drimostoma being found in Australia (Ann. Soc. Ent, Belg. 

 V0I.XY.). 



I have in my collection a single example each of two species 

 from the Northern Territory of S. Australia which appear to be 

 congeneric with Ahacetus australis, Chaud., but as the description 

 of that insect merely states the colour and then points out the 

 specific differences between it and R. flavipes, Thoms., (from 

 Gaboon), giving no account of the structural characters, I think I 

 shall do well to enumerate some of the characters of the present 

 insects to prevent any inconvenient results in case I should prove to 

 be wrong in supposing them congeneric with de Chaudoir's species. 



They both belong to the group which Lacordaire calls " Trigo- 

 notomides " having the mentum (which drops very abruptly below 

 the plane of the submentum and is separated from it by a strong 

 carina) narrowed forwards, with its front margin only sinuated. 

 The submentum is of peculiar structure, the middle part being a 

 flattened plate bearing three strong longitudinal carinas pointed in 

 front, on either side of which it (the submentum) becomes some- 

 what declivous and is limited by a curved keel ; the lateral por- 

 tions of the mentum have a crimped appearance. I have not been 

 able to examine the mentum satisfactorily except with a compound 

 microscope, but probably if a specimen could be spared for the 

 palpi to be removed it might be done with a Coddington lens. Of 

 the maxillary palpi the 2nd and 4th joints are subequal, the 3rd 

 being shorter ; the 2nd is depressed and dilated, the 3rd is 

 gradually dilated from the base to the apex and the 4th is nar- 

 rowed from the base to the apex, these palpi thus not differing 

 very much from those of Simodontus except in the second joint 

 being considerably more dilated. Of the labial palpi the 2nd joint 



