No- 9— 1856-8.] NEW CEYLON COLEOPTERA. 



49 



The points on which the three species which form this genus 

 more or less disagree are the following :— 



1) The labrum— is more transverse in 22. elegans and less 

 deeply emarginated in 22, ruficollis than in the other two 

 species respectively — still in all three it is emarginated, and 

 has moreover the peculiarity of being furnished with bristles at 

 the two anterior corners. 



2) The mentum — is subquadratically emarginated, the 

 lobes being strongly rounded on the outer side and abruptly 

 acuminated at the apex. At the base of the emargination it 

 is furnished with a broad, excavated tooth, which is inflected 

 and obtuse at the apex. So far all three species agree. 

 However, whilst in 22. elegans and rufieollis, this tooth is 

 slightly emarginated at the apex, it is sharply notched in 

 22". bimaculata, — in fact bilobed, the lobes being large and 

 rounded at the apex. I look upon this notch, which is sharp 

 but not deep, as a mere variation from the emargination 

 existing at the apex of the tooth of the two former species. 



3) The palpi — labial as well as maxillary have their ter- 

 minal joint truncated at the apex— and so far again all three 

 species agree. However, whilst this joint is of elliptic form 

 in the palpi of R. ruficollis , it is in R. elegans only so in the 

 labial ones, that of the maxillary ones being cylindric at the 

 base. In II. bimaculata finally, this joint is rather clubshaped 

 or subtriangular and more strongly truncated than in the two 

 former species. 



4) The ligula — is of subcoriaceous texture, middling size, 

 the shape of an oblong square, free and transversely truncated 

 at the apex. These characters are common to all three species 

 and in 22". ruficollis I have nothing to add to it. However, 

 the anterior margin, which is straight in this species, is 

 slightly bisinuated in H. elegans, the outer angles being 

 acute and the central one obtuse. The ligula of R, bimaculata 

 differs from both the former in as far as it is narrowed 

 towards the apex and depressed towards the sides and the 

 front, the anterior margin is otherwise cut away straight, 

 without any sinuosities, but it is rather strongly armed with. 



