944 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



THIKD SYNTHESIS. (TRIBES.) 



III. L— Tribe NOTERIDES. {Vide p. 260.) 

 This tertiary aggregate consists of two groups and two isolated genera, and 

 comprises altogether only about eighty species, arranged in nine genera. The size of 

 the individuals, occasionally very minute and never large, ranges from 1 to 8 m.m. 

 of lenoth. The form is peculiar, the convexity is great, but is nearly limited to the 

 upper surface ; the thorax and elytra are excessively co-adapted, and thus 

 perfectly continuous in outline ; this outline is attenuate or acuminate behind. 

 Varieoation of colour only occasionally becomes conspicuous, the punctuation of 

 the surface may be considerable, or on the upper surface may be wanting, giving 

 place to an extreme polish. The head is short, never in the least margined in 

 front, but terminating in a sharp edge, so that the very exposed labrum continues 

 the plane of the upper surface of the head ; the eyes are never very prominent, 

 and their circular outline is a little notched by the side of the head over the 

 insertion of the antenna. The antennee are short, and the shape of the joints is 

 more or less dissimilar inter se ; the labial palpi usually have the terminal joint 

 dilated, and frequently notched. The prothorax has always a lateral margin, which 

 is often very broad and very little elevated. The front coxse are conical in form 

 in some genera (Notomicrus, Hydrocoptus, Noterus), but approach more nearly to 

 the spherical form than in the other Dytiscidse, and in Suphisini and Hydrocanthini 

 they are nearly truly globose ; Pronoterus and Synchortus being apparently inter- 

 mediate forms in this respect. The pro.sternum along the middle longitudinally, 

 is usually of one plane from the front margin to the termination of the prosternal 

 process, but in Colpius, it is incrassate in this direction, so that it projects beyond 

 the coxpe, and forms a conspicuous prominent rectangle : the length of the pro- 

 sternum in front of the coxse is sometimes extremely little (Suphisini), sometimes 

 moderately great, (Noterus, Hydrocanthus) ; the prosternal process varies greatly, 

 but it has never a slender acuminate terminal portion, and is usually very large, 

 and becomes broader behind ; when small it is broad in proportion to the length ; 

 it is always received into a highly developed fork of the mesosternum, and its 

 posterior edge is extremely accurately co-adapted with the anterior part of the 

 inter-coxal process of the metasternum. 



The front legs are in the more difierentiated forms of the Noterides modified in 

 a remarkable manner, the modification reaches its extreme in the Suphisini and 

 Hydrocanthini, but little or no trace of it can be found in Notomicrus and Hydro- 

 coptus. Tiie femora in Suphisini become subcylindric and a little arcuate, and 

 the tibia assumes a position in which the normally upper face looks outwards ; this 

 part of the leg is at the same time modified in shape, and terminates in a large 

 hook ; this hook is one of the ordinary spurs of the apex of the tibia developed in 



