On Aquatic Carnivorous Coleoptera or Dytiscide. 209 
spicuous in the Carabidze and Cicindelide, In Pelobius theemargination of the labrum 
is destitute of the cilize found in most other Dytiscide. In Amphizoa the middle 
of the labrum appears from above rather prominent than emarginate, but whenlooked 
at from in front and beneath, it appears very much the same as in the ordinary 
Dytiscidze, but is destitute of the central series of ciliz. On the inner face of the 
labrum in the middle in front there is in the Dytiscidze a prominent triangular space, 
densely covered with pubescence, and this exists equally in Amphizoa, but is 
absent in Pelobius and the Noterides, while in the Carabidze the rule appears to be 
that there is a glabrous space on the middle of the labrum, with pubescence on 
either side, completely the reverse or what prevails in the Dytiscide. 
The mandibles are always short, and in the condition of repose nearly or quite 
concealed by the short labrum, they are very broad, their outer edge forms a very 
regular convex curve, while the upper and inner face is much twisted and is 
irregular in form, and the apex is turned into a broad somewhat sharp edge, which 
is a little prominent at each of its two corners ; the under surface is flat and bears 
along its inner edge a band of fine, dense, very short pubescence, and there is also 
usually an isolated patch of similar pubescence near the apex. 
The maxillee are provided with two lobes, the outer one of which is quite slender, 
and is divided a little below the middle so as to form a two-jointed palpus; the 
terminal joint is longer than the basal one, and is slender and cylindrical, usually a 
little acuminate towards the extremity, and the division between it and the basal 
joint is very perfect, so that the outer lobe of the maxilla is a perfect two-jointed 
palpus ; in Pelobius however the articulation between the two joints is imperfect, 
and the terminal joint instead of being cylindrical is broad and flat and has a large 
angular prominence on its inner edge, and an acute apex, so that the transformation 
of the maxillary lobe into a jointed palpus is very much legs complete in this insect 
than it is in the ordinary Dytiscidee ; in Amphizoa the outer maxillary lobe is curved 
and slender, but it is flattened and not cylindric, and the only trace ef a division is 
the existence of an emargination or notch on the inner edge, so that the condition 
of the outer maxillary lobe in this insect is very much that of the Gyrinide. The 
inner lobe of the maxilla is always strong and horny, and has an acute, bent 
inward termination, which plays the part of a hook in holding the food; this 
terminal portion is always free from ciliz, but the lower portion of the lobe, along 
its inner edge is always fringed with ciliz. These ciliz are subject to much 
difference in the family ; in Noterus there are only a few of them placed ata 
distance from one another, while in other cases (vide Eretes) they are dense and 
elongate ; on the upper face of the maxilla it may be seen that the inner lobe hag 
at its base internally a membranous or semicorneous space, and it is usually on 
this space that are placed the longest and finest ciliz ; it is rare that the cilize of 
the maxilla are very fine, but they are frequently very coarse, as may be seen in 
Dytiscus, where some of the terminal cilize are so stout as to form really powerful 
