276 A HISTORY OF FISHES 



of affairs which is very different when contrasted with the 

 invasion of South America by northern mammals and reptiles. 



The Ethiopian and Indian regions may conveniently be 

 considered together, as the fish-faunas of the two areas have 

 much in common. The relationship between the fishes of 

 South America and Africa has been already considered in 

 some detail, and it has been shown that in early Cretaceous 

 times these two countries formed a single continent. Now, this 

 continent must also have extended eastwards to India, but not, 

 as has been sometimes suggested, through Madagascar. The 

 order Ostariophysi must have originated and evolved in this 

 great land mass, and when it broke up at the end of the 

 Cretaceous period there were already primitive Cat-fishes and 

 Characins in both South America and Africa, and Cat-fishes 

 in India. The headquarters of the important family Cyprinidae 

 lay in Southern Asia, a region in which occurs a great number 

 and diversity of genera and species of these fishes, including 

 those which bear a marked resemblance to the Characins 

 from which they have clearly been derived. These ancestral 

 Characins must have come from Africa, and, as far as the 

 Indian region was concerned, were finally supplanted by the 

 more specialised Cyprinids. At the time that Africa became 

 detached from India it probably possessed no Cyprinids, and 

 the m.ultitude of species found in that country to-day, most of 

 which belong to characteristic Indian genera, are the result of a 

 comparatively recent immigration, when at the end of the 

 Eocene period Africa became joined with India to Eurasia. 

 Apart from the Carps, the other fishes common to India and 

 Africa include Cat-fishes belonging to three families, Laby- 

 rinthic-fishes. Spiny Eels (Mastacembelidae), etc. Among those 

 peculiar to Africa are the curious Mormyrids (Mormyridae) , 

 Bichirs {Polypteridae) , certain families of Cat-fishes, and the 

 toothless Moon-fishes {Citharinidae) , related to the Characins. 

 Apart from certain families of Cat-fishes there are no families 

 peculiar to the Indian region, but there are numerous genera of 

 specialised Carps, Suckers, Loaches, Labyrinthic-fishes, etc., 

 found nowhere else, and a single genus of Cichlids. 



The fish-faunas of the Palaearctic and Nearctic regions also 

 exhibit certain definite resemblances, such important fresh- 

 water families as the Carps (Cyprinidae), Pikes (Esocidae), Mud- 

 fishes (Umbridae), and Perches [Percidae) being common to 

 both (Fig. loi), although a number of characteristic North 

 American families are absent in the Old World. The Ostario- 



