The Primitive Fishes 287 



ganoids, the elasmobranchs Acanthodes and Pleuracanthus 

 still persist in great abundance, and mixed with amphibian, 

 reptilian and also plant remains. 



In his "Fauna der Gaskohle" Fritsch gives many sug- 

 gestive details regarding Pletiracanthus and the Acan- 

 thodii (2// : 3 : 48). To the latter group he adds the two 

 new genera Traquairia and Protacanthodes, as well as 

 describes small species of Acanthodes, on which, along 

 with freshwater crustaceans like Estheria and Gampsonyx, 

 Pleuracanthus largely fed. He consistently inclines to re- 

 gard the entire assemblage of plant and animal organisms 

 as being geologically of estuarine and brakish-water origin, 

 but absolutely no reason exists for such a position, specially 

 seeing that he mentions with them and describes amphibian 

 remains. 



While Pleuracanthus in several species was common 

 over wide freshwater regions of North America in Carboni- 

 ferous times, it also persisted there into the Permian, for 

 Cope has recognized its remains, and under the names 

 Diplodus and Didymodus he has described the teeth of it, 

 from the Permian of East Illinois and Texas {212: (1877) 

 192; (1884) 572). But a recent and valuable memoir is 

 "The Permian Fishes of North America" by L. Hussakof 

 (2/j) in which Janassa, Pleuracanthus, Diacranodus, and 

 Anodontacanthus are all treated of. He comments also 

 on the absence of Acanthodes from the rich Texan beds, 

 as compared with its presence in Europe, though he regards 

 the fossiliferous strata as possibly correlative. The entire 

 Permian fish series of North America is freshwater, and 

 we shall have occasion later to refer to the dipnoan and 

 ganoid inhabitants of it. 



Of special interest geographically is Woodward's paper 

 on the Hawkesbury fishes of Australia {214). In this he 

 describes Pleuracanthus parvidens from an extensive set 

 of freshwater deposits, that also contained dipnoans, cross- 

 opterygians and chondrosteans. Says he "this typically 

 upper palaeozoic shark has not hitherto been found in the 

 southern hemisphere. It occurs in the Carboniferous and 

 Lower Permian of Europe, and in the Coal Measures of 

 North America. Identical teeth have also been discovered 



