172 MICHIGAN SURVEY, 1908. 



"At the south, the Atlantic district merges through Florida into the Caribbean 

 tropical province, and through maritime Texas into the Mexican lower eastern 

 province. In the same direction the Central district merges into the Mexican 

 upper or central province, and the Interior district, towards the Gulf of Cali- 

 fornia, into the Mexican western province. Regarding the southern affiliations 

 of the Pacific district we know absolutely nothing; scarcely a single species 

 found at San Diego had been found in Mexico. 



"The method of distribution of species in the Atlantic and Pacific districts, 

 as already observed by me in various memoirs, is entirely different. In the 

 Atlantic district, a large number of species are distributed over a large extent 

 of country; many species are of rare occurrence, and in passing over a distance 

 of several hundred miles, but small variation will be found in the species 

 obtained. In the Pacific district, a small number of species are confined to a 

 small region of country; most species, occur, in considerable numbers, and in 

 travelling even one hundred miles, it is found that the most abundant species 

 are replaced by others, in many instances very similar to them; these small 

 centers of distribution can be limited only after careful collections have been 

 made at a great number of localities, and it is to be hoped that this very 

 interesting and important subject of investigation may soon receive proper at- 

 tention from the lovers of science on our Pacific shores. 



"In the Central district, consisting, as it does to a very large extent, of 

 deserts, the distribution seems to be of a moderate number of species over a 

 large extent of country, with a considerable admixture of local species; such 

 at least seems to be the result of observations in Kansas, tJpi)er Texas, and 

 Arizona." pp. III-V. 



1860. pp. 2-4. "The distribution of species in the northern part of the region 

 which furnishes the materials for this report [Pacific R. R. Report], presents no 

 remarkable phenomenon. As in other northern lands, certain tribes like Adephaga, 

 Staphylinidae, and Elateridae assume a greater predominance in the fauna, from 

 the fading out of the groups more characteristic of warmer climates, while a 

 greater 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 occurring on both sides of America is also largely 

 increased in these northern regions, but with the exception of Epiphanis cornutus 

 and Friognathus 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 Haplochile pygmaea, Ligyrus gibtosus, Alaus myops, and Microrhopala 

 vittata are the only representatives of America 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 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 proportion are not 

 found east of Kansas. Of American genera, AmilycUila cylindriformis, Lachno- 

 phorus elegantulus , and Eurmetopon atrium, are found in Kansas, or New 

 Mexico, while Ligyrus gibbosus and two species of Diabrotica also extend to 

 the Atlantic." 



"In Russian America the genera seems to follow 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 Russian America; of 



