XIV INTRODUCTION. 



next section, however, the Euschemones, we find a very decided con- 

 trast of plumage in the two sexes of certain species, and some differ- 

 ences in all, the blue and black of the male birds being replaced by 

 green and less decided tints in the females. The Gyrolce, which seem 

 naturally to follow, consist of three species only, each inhabiting its 

 own peculiar geographical district, and appearing not to intrude on 

 that of its neighbour. In this section, I believe, the adult males 

 and females are alike, the young birds being without the red on the 

 head, and the blue and golden tints which are characteristic of ma- 

 turity. Four black and blue species, constituting the group Eupre- 

 piste, seem best placed next after this. Here we have the sexes again 

 alike. The same rule obtains in the seventh and last section, for which 

 Cabanis' iexxnProcnopis is rightfully to be used, although he created 

 it only for one member of the group, a bird which in some respects 

 seems almost intermediate between the Procnopides and the Eupi'e- 

 pistcB. This is the most numerous in species of all the sections of the 

 genus, no less than seventeen of them being already known ; and it is 

 somewhat singular that not one of them is found in the eastern portion 

 of the S. American continent. With the exception of CallistcE larvata 

 a.nd francescce, which two nearly allied species are distributed to the 

 north of the Isthmus of Panama, the Procnopides appear to be met 

 with only in the slopes of the Andean ranges, and to be particularly 

 abundant in the mountain valleys of New Grenada. It is in this section 

 of Callistce that we may hope, as the tide of discovery progresses 

 through the still imperfectly known ranges of the great American 

 chain, for the discovery of rare and brilliant species yet unknown to 

 the Naturahst. 



But it will be interesting to review the general geographical distribu- 

 tion of the genus Calliste. The whole area occupied by the different 

 species of this form is nearly coequal with that tenanted by several 

 others of the characteristic groups of Tropical America, such as Gal- 

 hula, Cotinga and Pipra. Its limits will be seen at a glance by re- 

 ferring to the map which forms the frontispiece to the present volume. 

 It is, however, less extended northwards than that of others, such as 

 Momotus, Trogon and Tityra, which pass farther up the low coast- 

 lands constituting the " tierra caliente" of Mexico. As far as our 

 present knowledge goes, but one species of Calliste has yet been met 

 with within the limits of the Mexican States, namely, Calliste larvata, 



