On Aquatic Carnivorous Coleoptera or Dytiscide. 967 
characters in classifying the Coleoptera, and although the Hydroporides in the 
Dytiscidee, agree in this respect with the tetramerous Coleoptera, yet it is perfectly 
clear that this similarity of structure has been arrived at by perfectly distinct 
lines of descent ; and if we are not justified in considering this point of similarity 
in the Dytiscidze and Tetramera as evidence of community of descent between 
them, on what logical grounds is it that we may consider it as being such in the 
case of the various members of the Phytophaga ? 
The Dytisci complicati are found in all parts of the world, but in New Zealand and 
the Polynesian islands theyare, so far as is yet known, very pooriy represented, although 
Australia and Tasmania are very rich in species and genera. They appear to be 
remarkably tolerant of cold, the proportion of species found in high latitudes in 
the Northern hemisphere being remarkable: the series in this respect offers there- 
fore a great contrast to the Dytisci fragmentati, where the vast majority of the 
species are found in the warmer regions of the earth, and very few indeed, if any, 
penetrate to near the Arctic regions or are alpine in their habits. 
JP IIE INIBL -{S} WC IN| AD ella tS) Ibis\e 
The Family DYTISCID. 
The family as comprised in this work consists of the two unequal series, 
Dytisci fragmentati, and Dytisci complicati, the former consisting of only 175, 
the latter of about one thousand species. 
A detailed account of the external structure of the family has been given at the 
commencement of the work (pp. 190 e¢ seq.), and the definition of the family 
generalized from those details at p. 257. To complete the account it is necessary 
for me to make some remarks on the points of approximation or similarity between 
the Dytiscidze and other families of the order Coleoptera. 
The points of community between the Carabidee and Dytiscidee are so numerous 
and important, that it is not possible to point to any one character as an absolute 
test of distinction between the two families; and although several peculiarities 
may be pointed out as being especially characteristic of the Dytiscide, yet all of 
them when taken seriatim disappear within the bounds of the family or are found 
in one or more members of the Carabidz. These characters may be enumerated as 
follows: 1, the peculiar, continuous outline and solid compact form ; 2, the short 
broad head, immersed in the thorax as far as the back of the eyes and not 
narrowed behind the eyes ; 3, the glabrous antennw, free from setee and sensitive 
pubescence ; 4, the constant existence of a prosternal process ; 5, the fact that 
this prosternal process articulates, or rather connects with the metasternum; 6, 
the extremely large external lamina of the hind coxa; 7, the accurate adaptation 
