78 
BRITISH BEETLES. 
five-jointed, and the anterior and middle pairs either 
four or five-jointed. 
Dr. Sharp, in his most valuable monograph of the 
Dytiscidm (published in the Transactions of the Royal 
Dublin Society, 1880-2), divides the family into two 
great divisions, the Dytisci fragmentati and the Dytisci 
complicate. 
Iu the former of these divisions the episterna of the 
metathorax do not reach the middle coxal cavity; it 
contains two British genera, Laccophilus and Noterus, 
which have no visible scutellum, and in some points 
appear to bear a relation towards the Gyrinidas, their 
hind legs being much thickened. Noterus, also, has 
the antennae short, and much thickened ; being, more- 
over, of a somewhat similar build to Gyrinus, and 
having similar “jerky” habits. Species of both 
genera, also, occur in brackish water, a habitat of 
some of the Gy r ini. 
The second division, the Dytisci complicati, is by 
far the largest and most important; it is characterized 
by the fact that the episterna of the metathorax 
reach the middle coxal cavity ; in the tribe 
Hydroporina all our species have the anterior and 
intermediate tarsi four-jointed, whereas in all the 
other members of the division they are five- 
jointed. 
The Hydroporina are all small, with no visible scu- 
tellum, only four joints to the front and middle tarsi 
(often much widened) and the posterior coxrn enlarged 
in front. Some gaily-spotted species ( Hydroporus 
rivalis, Plate III., Fig. 3) are found in running waters, 
but the majority frequent ponds and lakes. Many 
have pubescent elytra; and the surface is usually 
