On Aquatic Curmnivorous Coleoptera or Dytiscide. 847 
Amphizoa shares the conditions of existence of Dytiscidee completely as regards 
the medium in which it lives, but only incompletely as regards its locomotion ; it 
lives in water constantly but does not move through the water, but clings to stones 
and moves about on them ; (the structure of its tibize and tarsi are of themselves 
sufficient to show that it is not a swimmer or diver) its legs however have not to 
overcome the influence of gravity, and they become forward propellers, not lifters, 
and they propel by pushing not against water, but against the surface of the stones 
beneath or behind them; the structure of these propellers is therefore a singular 
mélange of the structures of these parts in Dytiscidee and Carabidz, the coxee are 
modified absolutely in the Dytiscide direction ; while the other parts of the leg 
remain absolutely as in the lower Carabide. Strictly speaking therefore Amphizoa 
is neither Dytiscid nor Carabid. Nevertheless after this has been granted there 
presses itself on us this incontrovertible fact, viz., that in most of the points in which 
Amphizoa departs from Carabide it becomes Dytiscid, to which we must add the 
important fact that in the structure of its middle coxal cavities it possesses pecu- 
liarities found in no other beetles except itself and the Dytiscidee. Amphizoa is 
therefore for me a member of the Dytiscidee, that differs from all other members of 
the family by its want of means of swimming through the water, and occupies a 
completely isolated position in the family aggregate. 
Viewing the matter as a point of synthetical classification I assert boldly and 
without fear of contradiction this: that Amphizoa should be united with the 
Dytiscidze in a synthesis prior to the synthesis that unites together Dytiscide, 
Amphizoa, Carabidze, Haliplidee, and Cicindelidze as one aggregate. 
Dr. Horn has reviewed the opinions of Leconte, Lacordaire and Schaum, and stated 
(Ir. Am. Ent. Soc. 1867, p. 158), “with the Dytiscide, Amphizoa has but little in 
common excepting the large size of the posterior coxe. The parts of the mouth 
have but little analogy to those of Dytiscidee.” He gives however no further reason 
for its separation from Dytiscide; and I cannot myself consider that the parts of 
the inouth separate the insect from Dytiscide; the large size of the mentum is a 
fact of great interest but evidently of comparatively little importance; the only 
other point of difference in the trophi from Dytiscide is the absence of a division 
in the external lobe of the maxilla; but this point is merely a question of develop- 
ment, for I have no doubt it will be shown that all the primitive Dytiscidee (and 
Carabidz) had an inarticulate external lobe to the maxilla ; and moreover in the 
neighbouring family Carabide we tind that although the lobe is biarticulate in nearly 
the whole of its enormous number of species there are yet one or two exceptions in 
which it is only uniarticulate as in Amphizoa. Further, the parts of the mouth 
have not been examined in many Dytiscide, and it is quite possible that some true 
Dytiscidee may be found to have a simple external lobe on the maxilla, 
I come to the conclusion then, that Amphizoa cannot be considered a distinct 
family of Coleoptera from the Dytiscide and Carabidze, in the same sense as Dytiscidee 
