78 



Memoirs of the Indian Museum. 



[Vol. VII,. 



Protomocoelus resembles Labienus in having the lateral and intermediate areas of the 

 metasternum fused, though so far as I know the elytra are never united ; but it has the 

 dentition reduced, especially on the left side. It is probably allied to the asymmetrical 

 forms of Mastochilus through the more primitive species of Labienus {i.e., trigonophorus 

 and inaequalis) but does not appear to be allied to the higher forms of the latter 

 genus. 



Gonatas, with which the imperfectly separated Omegarius (? and Tatius of which I have 

 not seen a specimen) may be united, also tends to have the dentition reduced, especially 

 on the left side 



Pseudepisphenus and Tarquinius form the last line of descent from Mastochilus (s. lat.). 

 They are so unlike superficially that it seems best to retain both genera in the absence of 

 other forms throwing light upon them. Concerning their relationship see Gravely, 1914c. 

 pp. 328-329. 



The genera of Macrolininae may now be redefined thus : — ■ 

 The supra-orbital and supra-occipital ridges discontinuous ; 

 insects always symmetrical ; the mentum always with 

 primary but without secondary scars . . . . Macrolinus, p. 80. 



The supra-orbital and supra-occipital ridges continuous, the 

 latter sometimes produced outwards behind the former in 

 asymmetrical species without scars of any kind on the 

 mentum . . . . . . . . . . . . . . 2. 



The mentum without scars ; the outer side of the mandibles 

 angulate at the base or not at all . . . . . . . . . . 3. 



The mentum with scars ; or, the outer side of the mandibles 

 angulate opposite the anterior lower tooth . . . . . . . . 7. 



Only three lamellae recognizable when the antenna is furled ; the 



mentum strongly grooved in the middle line from front to back Pleurarius, p. 84. 

 More than three lamellae recognizable when the antenna is 

 furled ; the mentum at most with an incomplete median 

 groove anteriorly . . . . . . . . . . . . 4. . 



The inner tubercles separated by a space -|-J as long as that 

 separating the outer tubercles . . . . . . Tiberioides, p. 84. 



The inner tubercles separated by a space f-1 times as long as 

 that separating the outer tubercles . . . . .... . . . E_ 



' The left outer tubercle acute and little or no larger than the right ; 

 or, much larger and curved inwards, with its extremity rounded 

 rather than truncate and never angular on the outer side in 

 front. The dentition complete in symmetrical species ; the 

 lowest terminal tooth always present on both sides ; the 

 right anterior lower tooth smaller than the left in the more 

 highly asymmetrical species. The sides of the elytra hairless. Episphenus, p. 85. 

 The left outer tubercle larger than the right, directed more or less 

 inwards, truncate distally, the outer angle of truncation dis- 

 tinct, forming a more or less forwardly directed apex to the tu- 

 bercle ; or, the sides of the elytra hairy. The dentition complete, 

 or both the lowest terminal and anterior lower teeth reduced . . 6„_ 



