210 On Aquatic Carnivorous Coleoptera or Dytiscide. 
hooks. In Pelobius the ciliz are nearly entirely absent, the imner edge of the 
maxillary lobe bearing merely two short, fine sete ; in Amphizoa the cilize are 
abundant, and the lower portion of the lobe is furnished with dense fine pubescence, 
while the upper portion bears stouter cilize, a considerable space nearly free from 
cilize intervening between these two groups. 
The maxillary palpi are four jointed, the basal joint shorter than any of the 
others but quite distinct; the second and third joints are nearly similar to one 
another in length ; frequently the third is a little longer than the second ; the fourth 
joint is a little, or considerably longer than either of the others ; occasionally the 
terminal joint is notched or emarginate at the extremity (Noterides). The maxillee 
and their palpi are entirely destitute of any pubescence or setze (with the exception 
of the cilize of the inner lobe). The maxillee of the Dytiscidze are similar to those 
of the Carabidee, except in the absence of any outstanding setze and in the less 
elongate second joint of the palpi; in this latter respect the Pseudomorphini agree 
with the Dytiscidee. 
The mentum is a transverse corneous piece, of very hard consistency, articulated by 
a distinct suture with the piece behind it ; this suture is slighty curved or bisinuate, 
or nearly straight, but is quite obsolete in Amphizoa : the sides of the mentum are 
rounded in such a manner that the greatest width is at the base ; in front there isa 
large piece cut out of the middle for the reception of the ligula, so that the mentum 
is thus made to consist of two lateral lobes, projecting from a transverse basal 
piece ; the base of the excision is not straight, but projects farthest forwards in the 
middle, owing to the excision being deeper on each side in adaption to the piece 
supporting the labial palpus ; there is thus formed a slightly projecting, more or less 
distinct central lobe at the base of the excision ; this lobe is variable in form, and 
is usually short in proportion to its width, and with a rounded front edge ; but is 
sometimes emarginate in front ; when the labial palpi are approximate to one another 
this lobe is narrow ; or nearly absent (vide Deronectes) and may form a small acute 
tooth ; such a tooth exists in Noterus but has in that genus a bifid extremity. 
The side wings or lateral lobes of the mentum vary a little but not much in form ; 
in Hyphydrus their front termination forms a more acute and elongate angle than 
it does in other groups. In Pelobius the mentum is very much shorter than in any 
other Dytiscidee, so that the very broad excision is very short, and the very broad 
lateral lobes are extremely abbreviate ; in Amphizoa the mentum is remarkable for 
its large size, the basal transverse piece being very elongate, but in other respects 
it is formed as in the ordinary Dytiscide. 
The ligula is large and very conspicuous, it appears externally as a quadrate or 
transverse horny plate, filling up and projecting beyond the excision of the mentum : 
its free front margin varies a little in form, it may be nearly straight as in Cybister, 
or slightly rounded or even very feebly prominent in the middle, so as to be 
bi-emarginate, and is usually furnished with elongate very fine ciliz, placed some- 
