GEOLOGICAL DISTEIBUTION. 



201 



that of 0T1T period, many of our tropical genera occurring ia 

 localities which are now included within our temperate zone, 

 and being mixed with others, which nowadays are restricted 

 to a colder climate : a mixture which continues throughout 

 the Pliocene. 



A few families of fishes, hke the freshwater Salmonidse, 

 seem to have put in their appearance ia Post-pliocene times ; 

 however, not much attention has been paid to fish-remains of 

 these deposits ; and such as have been incidentally examined 

 offer evidence of the fact that the distribution of fishes has 

 not undergone any further essential change down to the 

 present period. 



[See E. Sauvage, Memoire sur la Faune Iclithyologique de la periode 

 Tertiaire. Paris 1873. 8°.] 



Fig. 102.— Py modus rhombus, a Ganoid from the Upper Oolite. 



