The larger specimen, first described, is divided into an upper and a lower half, the greater part, however, adhering to the lower slab. The bones adhere about equally to the two faces. The drawing is made from the lower slab, with some of the details filled in from the upper one. The feather impressions are about equally distinct on both, and where in either case the bones are absent, exact molds of them remain, so that the structure can be seen and measurements taken almost equally well from either slab, except that nothing anterior to the breast is shown on the upper slab.

The species here described is of special interest as being the first fossil Passerine bird discovered in North America, although birds of this group have been known for many years from the Tertiary deposits of Europe. The highest extinct ornithic type hitherto known from America is a Picarian bird (Uintornis lucaris) related to the Woodpeckers, described by Prof. O. C. Marsh in 1872, from the Lower Tertiary of Wyoming Territory. Probably the insect-bearing shales of Colorado will afford, on further exploration, other types of the higher groups of birds.

For the opportunity of describing these interesting specimens I am indebted to Mr. S. H. Scudder, who obtained them during his last season's (1877) explorations of the Florissant insect-beds. The specimens are now the property of the Boston Society of Natural History. My thanks are due to Mr. J. H. Blake for the great care with which he has executed the drawings.

In conclusion, I may add that in 1871 I obtained a few distinct impres sions of feathers from beds of the same age and from near the same locality. The first fossil feather, to my knowledge, discovered in North America was obtained by Dr. F. V. Hayden in 1869, from the freshwater Tertiary deposits of Green River, Wyoming Territory. This was described by Professor O. C. Marsh in 1870,* who refers to it as "the distal portion of a large feather, with the shaft and vane in excellent preservation".

* Am. Journ. Sci. and Arts, 2d ser., vol. xi, 1870, p. 272.

ART. XX.-THE COLEOPTERA OF THE ALPINE REGIONS OF THE

ROCKY MOUNTAINS.

BY JOHN L. LECONTE, M. D.

The elevated interior region of North America presents peculiarly favorable opportunities for the study of some of the most interesting questions connected with geographical distribution of animals and plants.

If the materials at our hands be, as indeed they yet are, a very scanty representation of the organic forms now living in that part of the continent, they are, at least, sufficient to indicate the direction in which investigations should be pushed, in order to arrive at definite and final results.

The peculiarly favorable circumstances to which I chiefly refer at present are dependent on the following points in the development of the region:

1st. The gradual enlargement of the land-surface at the expense of the circumambient seas during the latest Mesozoic periods.

2d. The gradual elevation of the middle of the continental mass during post-Cretaceous times, so as to greatly modify the climate in respect to both moisture and temperature. These changes have been so gradual, that we may say with certainty (excluding the local eruptive phænomena, which were more numerous, but not remarkably different from those of the present age) there has been no great or paroxysmal disturbance destructive of the land-surface in the elevated plains east of the Rocky Mountains since the deposition of our early Cretaceous strata (Dakota Group).

3d. While, during the Glacial epoch, the valleys of the mountains were filled with glaciers of moderate size, and the line of permanent ice streams and fields brought to a much lower level, there was an absence of the extensive ice sheets and flooded areas, which in Eastern America destroyed entirely the terrestrial organized beings of the former period. It must be inferred from the first and second of these premisses, that the new land exposed by this gradual development of the continent received its colonies of animals and plants from the conterminous older land-surfaces in various directions, and that the subsequent elevation of the continental mass, by which the moisture was diminished, caused a later invasion of the territory by those genera and species which are characteristic of arid regions.

We may also conclude, from the third premiss, that the glacial displace

ment of species in the Rocky Mountains has been much less than in Eastern America, and that a very small area would be left bare of life on the return to a normal temperature; consequently, the previous occupants of the higher mountains would again return to their former domain, increased by refugees from the circumpolar continent of temperate climate, driven southward by the increasing cold.

Such being the case, it ought to be possible, with well-prepared lists of the insects of the Plains and mountain regions, by comparison with lists of the local fauna of other zoological districts of the continent, to ascertain, with reasonable probability, the invasions from different directions by which, in the first place, the newly emerged land was colonized; and, in the second place, the modifications, either in distribution or in structure, which have subsequently occurred.

I have on another occasion* expressed my belief that the study of the distribution of existing insects could give much information concerning former topographical and geographical changes in the surface of the earth. I then gave several examples to show how the distribution of species peculiar in their habits and structure confirmed what was already known by geological investigation of the gradual evolution of the middle part of the continent. I will now advance the additional thesis, that we may obtain somewhat definite information of the sequence, extent, and effects of geological changes in the more recent periods by a careful study of the insect fauna in its totality.

While these pages were being prepared, I received from Mr. T. Vernon Wollaston a copy of his excellent volume on the small Coleopte. rous fauna of Saint Helena. This fauna, containing but 203 species, is remarkable for the large predominance of Rhynchophora, of the families Cossonide and Anthribidæ. It has, however, been greatly contaminated by the introduction, through commerce, of foreign species to the number of 74, or nearly three-eighths of the number now known to inhabit the island. The introduction of these 74 exotic species, in addition to the other changes produced by human agency, must have greatly modified the pre existing fauna, by repressing some and extinguishing others of the aboriginal species.

In the case of a portion of a continental area, such as is under consideration for my present purpose, the problems are by no means so simple. The human agency in the introduction of foreign species is slight. The *Trans. Am. Assoc. Adv. Science, 1875, Detroit, President's Address.

+ Since writing the above paragraph, I have been informed of the death of this most estimable and laborious investigator. The last of his publications was the memoir on the Coleoptera of Saint Helena, referred to in the text. The monographs of the Coleopterous fauna of the Atlantic Islands by Mr. Wollaston are among the most complete and exhaustive contributions to fa unal Entomology published. Their full importance can only be appreciated when more thorough investigations of the Beetles of the American and African Atlantic slopes are made and careful comparisons instituted. It will then be found that several genera of the Atlantides which do not occur on the other continent are represented in the American fauna.