During Triassic and Jurassic Periods 183 



evidence noted below, that has been gathered from the 

 Western Triassic region. 



The fishes recorded belong to the genera Semionottis 

 {Ischypterus of Egerton and Newberry), Catopterus, 

 Acentrophorus, Dictyopyge, Ptycholepis and Diplurus; 

 mainly members of the Chondrosteidae or sturgeon series. 

 While the genus Catopterus is, so far as known, peculiar 

 to Eastern American strata, Semionotiis and Dictyopyge 

 are common to Britain, Germany, Switzerland, South 

 Africa and Australia, Ptycholepis again includes seven 

 species, of which five occur in the Lias of England, one in 

 the Upper Trias of South East Europe, and one in the 

 Connecticut beds. Diplurus is a crossopterygian allied to 

 the more ancient Coelacanthus. 



Over western North America, as in Europe, an exten- 

 sive marine and a nearly as extensive freshwater, series 

 of deposits took place during Triassic time. The former 

 now covers a wide area from Alaska southward through 

 British Columbia, California and Nevada on through 

 Mexico and southward to Chile. Over all of this the 

 Triassic sea laid down typical marine strata with equally 

 typical marine organisms, that included foraminifera, 

 corals, echinoids and crinoids, univalve and bivalve mol- 

 luscs, an exceptionally rich variety of ammonites and other 

 cephalopods, but no recorded vertebrate life. 



The freshwater strata, as at present exposed, or left 

 after subsequent denudation, may have been developed more 

 or less continuously with the eastern deposits, over the 

 greater part of North America. Such a view is that in- 

 corporated in the chart of de Lapparent; and when we 

 think of the masses of freshwater strata now known to 

 occur in central and Northern Mexico, in North West 

 Texas, in Eastern California, and West Oklohoma there Is 

 much evidence in its favor. Not only so, a bridge In the 

 region of Honduras and eastward, may have connected 

 this northern expanse with a wide extension over eastern 

 South America. For in Brazil, the Argentine, and south- 

 ward to the Falkland Islands, wide areas exist where a 

 typical Triassic flora and freshwater or land fauna have 

 been traced. 



