252; On Aquatic Carnivorous Coleoptera or Dytiscide. 
The hind tibia is in the Noterides alone so long as or a little longer than the 
femur, but is sometimes much shorter (Cybister) ; this part varies extremely in its 
development ; in the feeble swiinmers (Hydrovatini, &c.,) it is elongate, many times 
longer than broad, and increases very slightly in diameter from the knee to the. 
extremity, a transverse section being nearly cylindric; in the higher forms, the tibia 
is much broader, and though when dissected off it is found to be always narrow at 
the knee, yet it attains its great breadth almost immediately below this, so that in 
Cybister, the articular cavity is situated on an extremely short neck placed at the 
anterior and outer extremity of the tibia; the tact that the greatest breadth of the 
tibia is gained immediately at the knee is characteristic of the Cybistrini, and the 
higher Hydaticides ; in the Dytiscini and Colymbetides, this abrupt spreading out 
of the tibia immediately at the knee does not occur, but the tibia increases in 
breadth by a gentle curve on its inner edge behind the knee, and gains speedily 
its greatest width near to the base, thence continues nearly parallel sided to the 
extremity, or indeed slightly diminishes in width towards the apex owing to a 
slight curving inwards of its outer margin. In Bidessus and Sternopriscus, the 
tibia is of peculiar form, being a little crooked owing to its being bent a little 
outwards some distance below the knee, and a slight bending outwards of the tibia 
likewise exists in many Hydroporides, especially in Colambus. Usually three 
faces are well defined on the tibia, viz. an upper, a lower, and an inner one, but 
in Cybister where the metamorphosis of the tibia is extreme, the inner face has 
entirely disappeared at the base, and is only tolerably well defined at the apex, 
so that the tibia in such case forms a flattened upper face, and a curved or slightly 
arched lower face; and in Hydrocanthus the tibize are so flattened that they 
form a plate whose two faces are only very slightly arched ; the lower face of the 
tibia shows a varied sculpture, being sometimes polished and with only a series of 
punctures placed near its outer edge (Noterides), sometimes dull and with a dense 
series of sete running its whole length parallel with the outer edge (Vatellini and 
many Hydroporini) sometimes densely punctate (Deronectes, group 1); but more 
usually the interior portion of the face is smooth and polished, while the exterior 
portion has large punctures bearing spines, (Cybister and many Colymbetides), while 
in other cases these large punctures have to a great extent disappeared but leave 
a marginal series along the outer margin; the outer and inner edges of the lower 
face of the tibia are armed with a series of spines. 
The upper face of the tibia bears, quite at the outer edge, elongate fine cilize or 
swimming hairs, which however are almost absent in Hydrovatus and Methles; its 
surface is, like the lower one, either polished or dull, but bears some large punctures 
furnished with spines, which assume a very remarkable development in the higher 
forms; the usual arrangement of these spine-bearing punctures is that there isa 
longitudinal series parallel with the outer margin, while the rest of the face external 
to this series may be quite smooth (Ilybius) or bearing numerous large, irregularly 
