XIV INTRODUCTION. 
is supposed to be supported by the occurrence in the Eocene of Wyoming and Utah 
of a fish, Priscacara, which has been referred by some authors to the Cichlide. 
But Priscacara has neither the reduced number of branchiostegals nor the toothless 
palate which characterize all living Cichlid, and it appears to me that it has no 
bearing on the problem of how two very closely allied genera, Acara and Paratilapia, 
differing from it and agreeing with each other in some important features which are 
obviously due to their near relationship, have come to inhabit South America and 
Africa respectively. 
DIstRIBUTION oF CICHLID®. 
The Indian Kéroplus is an isolated type, more specialized than Paretroplus of 
Madagascar, which appears to be its nearest relative, and, as has already been stated, 
a study of the American Cichlide leaves no possible doubt that the Mexican and 
Central-American Cichlid fauna has originated with immigrants from South America ; 
consequently the hypothesis of the northern origin of the family should, I think, be 
rejected. We are therefore led to believe that in early Eocene times Africa was 
connected by land with South America on the one side and with India, vid Madagascar, 
on the other. 
The Mexican and Central-American Cichlide number about 65 species; they are 
