Oii A<2(ialio iJainiL'orous Coieoptera or DytiscidcE. 847 



Amphizoa shares the conditions of existence of Dytiscidse completely as regards 

 the medium in which it Hvos, but only incompletely as regards its locomotion ; it 

 lives in water coustanLly but does not move through the water, but clings to stones 

 and moves about on them ; (the structure of its i\h\se 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 

 melange of the structures of these parts in Dytiscidae and Carabidse, the coxae are 

 modified absolutely in the Dytiscidse direction ; while the other parts of the leg 

 remain absolutely as in the lower Carabidae. Strictly speaking therefore Amphizoa 

 is neither Dytiscid nor Carabid. N^evertheless 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 Cai-abidai 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 Dytiscidse. Amphizoa is 

 therefore for me a member of the Dytiscidse, 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 Ampliizoa should be united with the 

 Dytiscidse in a synthesis prior to the synthesis that unites together Dytiscidse, 

 Amphizoa, Carabid £e, Hahplidse, and Cicindelidse as one aggregate. 



Dr. Horn has reviewed the opinions of Leconte, Lacordaire and Schaum, and stated 

 (Tr. Am. Ent. Soc. 1867, p. 158), "with the Dytiscidse, Amphizoa has but little in 

 common excepting the large size of the posterior coxse. The parts of the mouth 

 have but little analogy to those of Dytiscidse." He gives however no further reason 

 for its separation from Dytiscidse ; and I cannot myself consider that the parts of 

 the mouth separate the insect from Dytiscidse; the large size of the mentum is a 

 fact of great interest but evidently of com2:)aratively little importance; the only 

 other point of difference in the trophi from Dytiscid^ 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 ail the primitive Dytiscidse (and 

 Oarabida^) had an inarticulate external lobe to the maxilla ; and moreover in the 

 neighbouring family Carabidse we find 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 Dytiscidse, and it is quite possible that some true 

 Dytiscidse 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 Coieoptera from the Dytiscidse and Carabidse, in the same sense as Dytiscidse 



