INSECTS COLEOPTERA 3 



number of species are found common to both continents. Of these latter, about one half are 

 found on the Atlantic slope of America, while the other half have not yet occurred there. 



The number of species occuring on both sides of America is also largely increased in these 

 northern regions, but with the exception of Epiphauis cornutus and Priognathus monilicornis, 

 the genera of such species are distributed on both continents. 



On proceeding southwards to Oregon (and Washington Territory, which is, for purposes of 

 convenience, always included when Oregon is referred to in these pages) similar phenomena 

 may be observed, though on a diminished scale. The species of the eastern continent, not 

 found on the Atlantic slope of America, have entirely vanished, and of the species common to 

 both sides of both continents, but four remain. The number of species common to the Atlantic 

 and Pacific slopes of America has greatly diminished, and among them Haplocliile pygmaea, 

 Ligyrus gibbosus, Alaus myops, and Microrhopala vittata are the only representatives of American 

 genera. 



Finally reaching California, the species common to the two continents are reduced to Silpha 

 lapponica and Dermestes vulpinus, the species common to Atlantic and Pacific America have not 

 diminished absolutely in number, but from the more complete and copious fauna known to us 

 their relative proportion is much lessened. Among them, however, are found but few which 

 extend their range to the Atlantic States proper, while the greater ])roportion are not found 

 east of Kansas. Of American genera, Amblychila cylindriformis, Lachnophorus elegantulus, and 

 Eurymetopon atrum are found in Kansas, or New Mexico, while Ligyrus gibbosus and two 

 species of Diabrotica also extend to the Atlantic. 



Having thus passed in rapid review the distribution of species, as illustrated by tables III 

 and IV, the much more important subject of the distribution of genera remains to be considered. 

 The phenomena afforded by the study of seven of the most numerous families, I have endeavored 

 to express in a numerical form in tables I and II. 



In Kussian America the genera seem to ibllow to a certain extent the course already pointed 

 out of the species, that is : the genera common to both continents have a much greater relative 

 proportion, and among them a by no means insignificant part have not yet been found in 

 Atlantic America ; but as some of them are characteristic of high northern latitudes, there is 

 reason to believe that the number will be reduced by more thorough explorations in Labrador, 

 Newfoundland, and the regions near Hudson's Bay. 



Of genera confined to America, but six or seven occur in Eussian America ; of these but 

 three, Pristodactyla, Epiphanis, and Priognathus, have been detected on the Atlantic slope. 

 Pristodactyla might, indeed, be for the present excluded from the list of peculiar American 

 genera, for two reasons : 1, a certain number of species classed by Dejean, with Agonum, and 

 remarkable for having but two dorsal punctures, are in reality Pristodactylae, and until the species 

 of Siberia are thoroughly revised, we are warranted in supposing that some of them may also 

 be included ; but^ 2, because the distinctions between Calathus and Pristodactyla, as observed 

 by Lacordaire, are hardly sufficient to warrant the retention of the latter genus. 



In Oregon the eastern genera, not found in the Atlantic States, have diminished in number, 

 but among them occurs Callisthenes, which is found in Kansas. The number of American 

 genera has largely increased, even with our limited collections ; of them 14 are found in the 

 Atlantic States, 2 in Kansas, while 8 are peculiar to Pacific America ; of the 14 found in the 

 Atlantic States, Haplochile, Dichelonycha, Anelastes, and Alaus are the only ones not found 

 within the tropics. 



