Eastman; Tertiary Fish Remains. ■'>'■'> 



are described by Dr. Eigenmann as follows: " This land-mass sank 

 beneath the surface of the ocean, forcing the fauna in two directions, 

 towards Africa and towards South America, exterminating all types 

 not moved to the east or the west. From these two rudiments 

 have developed the present diverse fauna? of Africa and South Amer- 

 ica, each reinforced bj intrusives from the ocean and neighboring 

 land areas by autochthonous development within its own border. 

 The one fauna cannot be said to have been derived directly from 

 the other. The connection between Africa and South America existed 

 before the origin of the present genera and even before the origin of 

 some of the present subfamilies and families, some time before 

 the earlier Tertiary. There has never been any exchange between 

 Africa and South America since that time." 3 



Elsewhere in the same article the author whom we have just quoted 

 remarks: " There has been a remarkable parallelism in the evolution of 

 genera of cichlids, characins, and catfishes on the two continents. . . . 

 The Cichlida? are abundant in tropical America and Africa, a few 

 species of Cichlidae being also found in India. There is no means 

 by which these two forms could have crossed the existing gap between 

 Africa and South America. There has been no exchange of species 

 in recent times, for there is no species or genus common to the two 

 continents. The South American and African elements of these two 

 families must have been derived from some intermediate land-mass 

 or must have gone from one continent to the other over a land-bridge." 



It may not be amiss to consider here somewhat briefly the present 

 and former distribution of the genus Diplomystus, which is a typical 

 example of the double-armored herrings. Diplomystus dentatus, the 

 type species, w-as described by E. D. Cope in 1877 from the Middle 

 Eocene (Green River) fresh-water deposits, and at the same time 

 two previously described Clupeoids which accompany it in the same 

 horizon and locality were transferred to the new genus. These were 

 the so-called Clupea humilis and C. altus of Leidy. Cope recognized 

 thai the species comprised by Diplomystus might be divided into two 

 sections, distinguished by the form of their dorsal ridge-scales. " In 

 section I," he observes, " these shields are transverse and their 

 posterior borders are pectinate, a median tooth being especially 

 prominent. In section II, the scuta are not wider than long, and 



3 Eigenmann, C. H., The Fresh-water Fishes of South and Middle America 

 Pop. Sci. Monthly, Vol. LXVIII, No. 6, 1906, p. 528. 



