248 On Aquatie Carnivorous Coleoptera or Dytiscide. 
in the males of the Hydaticides both spurs are absent on the frent legs. In the 
Noterides the front tibise undergo a modification of form, which attains its 
maximum of development in Suphis, where the tibia is changed in position owing 
to a twisting of the leg, the front face being turned outwards; the anterior spur 
is developed into a thick, elongate, very curved, acuminate process, and being 
apparently soldered to the tibia gives rise to the appearance of a hooked tibia ; 
the tarsus is inserted on the inner (now. the lower) edge of the tibia just under a 
large prominence. In other members of the Noterides modifications similar to 
this may be traced, the most constant feature being the large curved anterior (or 
lower) spur; the structure of the primitive Noteride tibia still exists in 
Pronoterus, where we find a short very broad triangular tibia, with a rather small 
strongly curved spur at its inner angle. A very highly modified front tibia is 
found in the male of Eretes, where it is formed so as to allow of a maximum of 
rotatory motion over the tarsus when this is firmly fixed. 
The anterior tarsi of the Dytiscidee belong to three quite distinct types; in one 
of these they are five-jointed, the joints being more or less cylindrical and armed 
beneath with spines, between which the surface is shining and polished ; the four 
basal joints differing little inter se in length, the fifth more elongate ; this structure 
is however greatly obscured in the males as these in many species have the three 
basal joints dilated, sometimes enormously dilated, and clothed beneath with peculiar 
hairs or cups; the number of joints is however always distinctly five: the 
Laccophilini, Amphizoa, Colymbetides, Dytiscini, Hydaticides, and Cybistrini 
possess tarsi of this structure, which is in fact, except as regards the extreme 
development in the males, that which exists in the Carabide. The second type of 
structure of the front tarsi is likewise a pentamerous or five-joited one, and the 
tarsi are spinose beneath, but they have the basal joint very much larger than the 
others, and greatly compressed laterally, that is to say the joint is very deep from 
its upper surface to the sole, this latter being narrow ; this form of tarsus is peculiar 
to the Noterides ; the male tarsi though often a good deal larger than those of the 
female, are never highly modified, and they have only a very few cups on their 
under surface. The third form of tarsus exhibits only four joints, and of these the 
basal three are very different from the terminal one, being more or less broad and 
flat so as to present beneath a flat sole, which is without spines but bears a dense 
spongy pubescence, the third joint is more or less deeply emarginate or bilobed, 
while the fourth or terminal joint is slender and cylindrical ; the male feet are not 
ereatly different from those of the female, although frequently a good deal broader. 
This form of tarsus is found in the Hydroporides and Vatellini, and is not only in 
respect of the number of joints a tetramerous tarsus, but is essentially as regards 
both the form and clothing of the joints similar to what exists in the Tetramerous 
or Phytophagous (as opposed to the Carnivorous) Coleoptera. 
The modifications shown in the structure and development of the male tarsi in 
