FOSSIL BUTTERFLIES. 759 



as closely as to anything, to a tropical American group of l)Utterflies geo- 

 graphically isolated, all of its iinnicdiate relations being East Indian. Of 

 none of the butterflies to which all of these Nyniphalinae are allied is the 

 food plant of the caterpillar known. 



The sixth Nymphalid, Prolibythea, is of special interest, for it belongs 

 to the curious subfamily Libytheinae of which only a dozen species are 

 known. No group of butterflies exists with so many anomalies of struc- 

 ture ; none, so fiir removed from its nearest neighbors, which is anywhere 

 nearly so poverty-stricken in forms. It is a clear case of a waning type ; 

 and that out of the paltry dozen or two of fossil butterflies one sliould l^e 

 found to belong to a type which cannot number more than a tenth of one per 

 cent of living forms is indeed a surprise. It has a further interest, for the 

 existing OldVorld forms of this group and those of the New are separated 

 by characters which are unmistakal)ly combined in this fossil, though on 

 the whole the relations of the fossil are rather with the Old AVorld than 

 with the New World type, and especially with a form from AVestern 

 Africa. The group as a whole is distinctly tropical and subtropical and 

 wide spread, so that the subtropical aspect of the previously known Flor- 

 issant forms is not disturbed. The food of the larva, so far as known, is 

 exclusively Celtis, and it is interesting to note that Lesquereux has found 

 among the plants of Florissant, in the same beds with Prolibythea, two 

 perfectly well preserved leaves of a very fine Celtis, whose generic relations 

 are positively ascertained ; with them were also found fragments of flowers 

 which could have been readily admitted as of the same species. It is 

 therefore highly probable that Prolibythea vagabunda fed on Celtis 

 maccoshi Lesq. 



The last American fossil is Stolopsyche, one of the Pieridi, more nearly 

 allied to Pieris proper, including our New England species, P. oleracea 

 and the imported P. rapae, than to any others ; it is not very nearly re- 

 lated, and wherein it departs from these it comes nearer to some sub- 

 tropical forms. Little, however, can be said concerning it, and nothing of 

 its probable food plant can safely be surmised. 



The aspect of the Florissant butterfly fauna is therefore distinctly 

 southern ; and while tertiary America does not fully return the compliment 

 tertiary Europe seems to pay it, there is a certain Old World aspect in the 

 representative of that gypsy-type, the Libytheinae. 



There are one or two points further in our American fossil butterflies 

 which it is interesting to note. In two or three of them the structure of 

 the front legs can be determined and we are able to note that in this 

 oligocene tiine, among the earliest butterflies that have come down to us, 

 we\ave the same structure of the female fore leg in Libytheinae that we 

 have to-day. As this is one of the present stumbling blocks of the system- 

 atist it is well to draw attention to it. The more particularly, as the 



