4 U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY 47TH PARALLEL 



In California the genera of the eastern continent have increased absolutely, from more exten 

 sive collections, over those found in Oregon, but do not attain the same relative proportion as 

 those found in Russian America ; among them is one, Tryssus, a genus heretofore known only 

 from Madagascar, and is thus far the sole representative of the tribe of Scarabaeidae, to which 

 it belongs on this continent. 



The number of American genera has greatly increased, partly by the addition of genera found 

 within the tropics, and partly by the introduction of a few peculiar genera ; the most remark 

 able addition, however, is that of eighteen genera of Tenebrionidae, of which but two, Nosoderma 

 and Blapstinus, extend into the Atlantic States, while only four others extend into Kansas or 

 New Mexico. The genera found in the Atlantic States, and not in the tropics, are Thalpius, 

 Axinopalpus, Dichelonycha, Anelastes, Perothops, and Melanactes. 



Another fact of great interest is the distribution of species within narrow limits observed in 

 California. I am not able to exhibit the results in a tabular form, as collections have not been 

 made with minuteness at a sufficient number of localities to give any definite results, but I can 

 merely state my own experience, that but few species occurred at more than one place, and call 

 attention to the fact that, in every collection made at a fresh locality, a large proportion of new 

 species is found, while in Oregon, at points equally distant from each other, a greater unifor 

 mity is seen. 



The analysis, therefore, conducts to the same results announced by me, in 1851, at the meeting 

 of the American Association for the Advancement of Science ; the fourth proposition was, 

 unfortunately, announced in too absolute terms, as the only two genera then known to me, 

 Thalpius and Axinopalpus, were not considered as of sufficient importance to modify the result. 

 Thalpius, indeed, is so closely allied to Diaphorus, that we may well expect some of the species of 

 the latter genus to belong to it, while Axinopalpus is by many entomologists not separated 

 from Dromius. The other four American genera common to California and Atlantic America, 

 not found in the tropics Dichelonycha, Anelastes, Perothops, and Melanactes upon which I 

 am now obliged to modify the assertion, were subsequently obtained. 



The four propositions stated by me in the essay mentioned are : 



1. California constitutes a peculiar zoological district, with sufficient relation to the other 

 districts of America to prove that it belongs to the same continental system. 



2. This zoological district is divided into several sharply defined sub- districts, having a very 

 close resemblance to each other. 



As the same mode of distribution obtains in the groups of islands adjacent to the western 

 coast of America, we are led to believe 



3. That the local distribution of a small number of species is the characteristic of the eastern 

 Pacific region, as the extensive distribution of a large number is the prevailing feature of the 

 Atlantic basin . 



4. The genera occurring in, but not peculiar to, this district belong to two classes : either 

 (with the exception of Ergates) they occur on the Atlantic slope of both continents, or, if peculiar 

 to America, they are (with the few exceptions above noted) also found within the tropics. 



[NOTE. The Coleoptera collected by me at San Diego and other localities in the southern part of California have not been 

 included in this report, as they more properly belong to the fauna of the Mexican Boundary, and will be contained in the 

 report of the survey made by the Boundary Commission.] 



