On Aquatic Carnivorous Coleoptera or Dijlisciche. 203 



spicuous in the Carabid^e andCicindelidee. InPelobius theemarginationof the labrum 

 is destitute of the cilise found in most other Dytiscidfe. In Amphizoa the middle 

 of the labrum appears from above ratherproniinent than emarginate, butwhenlooked 

 at from in front and beneath, it appears very much the same as in the ordinary 

 Dytiscidfe, but is destitute of the central series of ciliaj. On the inner face of the 

 labrum in the middle in front there is in the Dytiscidee a prominent tiuangular space, 

 densely covered with pubescence, and this exists equally in Amphizoa, but is 

 absent in Pelobius and the Noterides, while in the Carabidse 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 of what prevails in the Dytiscidae. 



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 verv 

 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 ils 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 maxillaj 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 less complete in this insect 

 than it is in the ordinary Dytiscidse ; in Amphizoa the outer maxillary lobe is curved 

 and slender, but it is flattened and not cylindric, and the only trace of 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 Gyrinidaj. 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 ciUse, but the lower portion of the lobe, along 

 its inner edge is always fringed with ciliae. These ciliaB are subject to much 

 difference in the family ; in Noterus there are only a few of them placed at a 

 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 has 

 at its base internally a membranous or semicorneous space, and it is usually on 

 this space that are placed the longest and finest ciliae ; it is rare that the cilise of 

 the maxilla are very fine, but they are frequently very coarse, as may be seen in 

 Dytiscus, where some of the terminal ciliae are so stout as to form really powerful 



