ECOLOGY OF ISLE ROYALE. 173 



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 

 d,nd 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, ^lave dimin- 

 ished 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. 



"In California the genera of the eastern continent have increased absolutely, 

 from more extensive 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 ad- 

 dition of genera found within the tropics, and partly by the introduction of a 

 few peculiar genera; the most remarkable 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, Axindpalpus, 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 ex- 

 perience, that but few species occurred at more than one place, and call at- 

 tention 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 uniformity is seen. 



"The analysis, therefore, conducts to the same results announced by f 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 to 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 en- 

 tomologists not separated from Dromius. The other four American genera com- 

 mon 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 mentioned by me in the essay mentioned are: 



1. California constitutes a peculiar zoological district, with sufficeient rela- 

 tion 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 character- 

 istic 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." pp. 2-4. 



This paper is accompanied by four tables as follows: 



23 



