368 Evolution and Distribution of Fishes 



ina and other genera, passage of these eastward to Europe 

 along the N. Atlantis shore, and evolution of new genera, 

 alike in N. American, European, and later in Asiatic seas, 

 then proceeded. But these marine genera, which include 

 Kirtlandia, Atherinopsis and Basilichthys of American 

 waters, Iso of Japanese waters, and Atherinosoma of 

 Australia are nearly always more specialized in structure 

 than are the freshwater types. 



The small family of the Ophiocephalidae probably is 

 an evolved and modified offshoot from freshwater forms 

 of the last which passed from American lakes — where they 

 are now absent — along the northern borders of the S. 

 Atlantis bridge to Africa and later to Asia. While 3 species 

 of Ophiocephahis are now found across tropical Africa, 25 

 species are scattered eastward across Asia, and the only 

 other genus Channa includes 3 species from Ceylon to 

 China. The absorption of the ventral fins and of pyloric 

 appendages in the latter genus, indicates that it has become 

 modified along devolving lines during its passage eastward. 

 It would be of interest to learn what environal factors 

 have operated to produce such results. 



The Mugilidae is represented in the lower freshwater 

 Oligocene of Aix-en-Provence and similar central European 

 strata by species of MiigiL But they must have existed even 

 earlier over a wide area. For land connection must still 

 have persisted between Europe and America to permit the 

 presence of freshwater genera in the latter country. Re- 

 garding two of these Jordan says : "The genus Agonostomus 

 includes freshwater mullets of the mountain rivers of the 

 East and West Indies and Mexico, locally known as trucha 

 or trout. A. nasutus of Mexico Is the best-known species. 

 The Toturo or Bobo, Totiirtis pichardi, is a very large ro- 

 bust and vigorous mullet, which abounds at the foot of 

 waterfalls in the mountain torrents of Cuba, eastern 

 Mexico, and Central America." 



From its structural characters we would regard Agono- 

 stomus as more primitive and simple than Mugil or Myxus, 

 for the absorption of teeth, the mode of feeding, and the 

 related pharyngeal modifications, the complicated stomach, 

 as well as the numerous points of skeletal advance in Mugil 



