INTRODUCTION. 9 
rissant, the Florissant or LacusTrinE FAUNA. Which of them is the older can 
not be determined until their faunas have been more completely studied; 
and even then, for lack of sufficient comparisons elsewhere on the conti- 
nent, it may be impossible from the insect remains alone to reach any pos- 
itive conclusions. When the structure of the Green river beds has been 
more completely studied, their age can doubtless be determined with much 
accuracy; and a similar result may be reached when the age of the oro- 
graphic movement shall have been determined which brought about the 
emptying and desiccation of the ancient Florissant lake. With these time 
elements given, the extent of the insect remains in the Gosiute and Lacus- 
trine faunas is such that the relations of deposits hereafter discovered may 
quickly be made clear. 
The difference between the Gosiute and Lacustrine faunas is shown 
to be much more remarkable when we examine the larger groups. Thus, 
of the 66 genera found at Florissant, only 18 occur also in the Gosiute 
fauna, which contains, besides, 31 genera not found at Florissant, and there 
are even a number of tribes which, as far as we yet know, are entirely 
confined to one or the other fauna. 
Besides the beetles described or enumerated in this work, no fossil 
Rhynchophora have been described from any formation, Tertiary or pre- 
Tertiary, on the American Continent, with the single exception of a species 
of Curculionidz which I have called Hylobiites cretaceus' and which was dis- 
covered in the Pierre shales of the Assiniboine river, northwestern Manitoba, 
by Mr. J. B. Tyrrell, of the Canadian Geological Survey, in 1888. 
In conclusion, the following statements may be made regarding the 
Rhynchophorous fauna of the American Tertiaries in general : 
(1) The general facies of the fauna is American, and somewhat more 
southern than its geographical position would indicate. 
(2) All the species are extinct, and though the Gosiute lake and the 
ancient lacustrine basin of Florissant were but little removed from each 
other, and the deposits of both are presumably of Oligocene age, not a single 
instance is known of the occurrence of the same species in the two basins. 
(3) No species are identical with any Kuropean Tertiary forms. 
‘Cont. Can. Paleont., u, 30-31, pl. 1, fig. 5. 
