Distribution of Primitive Fishes 489 



The oldest Eugnathidae like Heterolepidotus, Allolepi- 

 dotus, and Ptycholepis had already spread, as freshwater 

 genera in Upper Triassic time, from east and S. E. Europe 

 westward to Britain, and in the last genus to at least Con- 

 necticut. The two first persist into the Lias. Caturus, that 

 is as yet only known from Central-South European strata 

 of Triassic age, is there continued through the Liassic and 

 Kimmeridgean into Purbeck beds. It can safely be assumed 

 then that the family lived and gradually evolved, over a 

 land area that at one time or another connected from S. 

 E. Europe to Connecticut. Whether the more recent 

 Neorhomholepis and Lophiostomus that pass into upper 

 Cretaceous rocks, are wholly freshwater, or anadromous, 

 or even marine, seems at present doubtful. 



The Semionotidae evidently originated and continued as 

 a freshwater group. It also is suggestive as to the disposi- 

 tion of land masses from the period of the Upper Permian 

 when Acentrophorus is first known from Durham, England 

 east to Bohemia. Through the succeeding Bunter, Keuper 

 and Rhaetic rocks of the Triassic, the family became ex- 

 tremely abundant and widespread in such genera as Semi- 

 onotiis, Serrolepis, Pristisomiis, and Colobodus. These, 

 along with smaller genera, indicate that land areas for their 

 dispersion must have existed from parts, if not most, of 

 the Eastern American States across to central-south Europe, 

 thence across South Germany to Italy and into the Karoo 

 region even of S. Africa. A possible offshoot from one or 

 other of the two last seems to have spread across the 

 Triassic Gondwana continent into Australia, and there be- 

 came modified into the species of Semionotus, Aphnelepis, 

 and Pristisomiis, that are found in the Lower and Upper 

 Hawkesbury-Wianamatta beds of N. S. Wales. 



With the evolution of more recent genera like Cleithro- 

 lepis, Aetheolepis, Dapedius, Tetragonolepis, and Lep'i- 

 dotus, that extend from Upper Triassic to Wealden or 

 Upper Jurassic time, the above geographic area was not 

 only persisted in, extensions were made into India and S. 

 Siberia over the Eurasian continent of that time. The re- 

 quired land and freshwater facilities for the above distri- 

 butional passages would be amply met, were we to accept 



