LOWER LIP. 257 



Mr. Newman calls it mentum and insertio, and regards it 

 both as a terminal part of the throat, and as a basal part of 

 the lower lip, at least if I understand him correctly, which 

 it is certainly difficult to do, from the abrupt manner in 

 which his definitions of these organs of the mouth are drawn 

 up. The chin, or mentum (the broad horny plate above 

 mentioned), is very variable in its form (ch or c 2), some- 

 times, as in the lamellicorn beetles, serving exactly as a lower 

 lip, and closing the mouth ; but in other beetles it is shorter 

 and more transverse, and cannot be in the least degree 

 effectual in performing this office. Sometimes even its base 

 is soldered to the jugulum, the stipes being entirely obsolete, 

 and thus, in fact, becoming the anterior edge of the former. 

 This is the case in Paussus, Siagona, &c. ; but its true 

 nature may be known by the position of the labial palpi, 

 which always arise between its extremity and the base of the 

 terminal portion of the lower lip, to which (if with MacLeay, 

 Kirby, Curtis, &c., we continue the analogy with the human 

 face) we must restrict the name of lower lip or labium, al- 

 though the same name is also applied to the whole apparatus. 

 This difficulty may be obviated by terming this piece, with 

 Fabricius and others, ligula. The latter piece is more mem- 

 branous, and of a smaller size than the mentum, and often 

 serves to close the mouth as effectually as the former. I 

 therefore see no sufficient reason, on this account, for not 

 giving to it the name of the labium, or lower hp. The form 

 of this organ is very variable, and sometimes, as in the 

 tiger-beetles, it is completely concealed by the mentum. 

 On examining the lower lip internally, a distinct mem- 

 branous or leathery lining (t) will often be found, the angles 

 of which are protruded beyond the front margin of the lower 

 lip, in the form of little protuberances (t t). These are very 

 conspicuous in many Carabidce, and are termed paraglossae, 

 although they can only be regarded as the produced angles 



z.3 



