THE PERMIAN FISHES OF NORTH AMERICA 



175 



COMPARISON OF THE PERMIAN FISH-FAUNA OF 

 AMERICA AND BOHEMIA. 



In the accompanying table the Permian fishes of IlHnois, Texas, and 

 Bohemia are brought together for comparison. It is seen that of the two 

 American localities the Texan is the richer in genera — 12 as against 6 for 

 Illinois. The Illinois fauna is entirely represented in Texas with the excep- 

 tion of one group — the PetalodontidcE, a family of sharks represented in 

 Illinois by the genus Janassa; but as this genus is known only from small 

 teeth, which may easily be overlooked in collecting, it is probable that it 

 may yet be discovered in the Texan formations. However this may be, 

 there is a remarkable agreement between the two faunas considering the dis- 

 tance by which they are separated. 



Table showing Genera of Fishes in the Permian of Illinois, Texas, and Bohemia. 



' Based on the list given by Fritsch in Sitzungsb. d. k. bohm, Gesell. Wiss., 1895, pp. 12 et seq. 



A comparison of the Permian faunas of Texas and Bohemia brings out 

 several interesting points. While the groups represented in the two are, 

 with the exception of the Acanthodii, the same, there is a marked difference 

 in the genera respectively represented, proving the long segregation of 

 the two stocks from which the Permian faunas of the two localities are 

 descended. The most remarkable difference between the faunas is the 

 presence of Acanthodii (three genera) in Bohemia and their absence in 

 Texas. The Acanthodii occur in Bohemia at the same level as Pleuracanthus, 

 a horizon which may be correlated approximately with the Texas and 

 Illinois horizons. 



