The Chondrostei and Holostei 323 



life, a continued deposit of the dust took place to form 

 the non-fossiliferous bed. 



Woodward also draws attention to the fact that while 

 the European species of Coccolepis were small, C. australis 

 was a fairly large fish that measured about 13 inches. It 

 was accompanied by other "ganoids" belonging to the 

 Semionotidae, Pholidophoridae, and Leptolepidae, all of 

 which are treated subsequently in this work. 



The Palaeoniscidae then, from Lower Old Red to 

 Mid Jurassic days, were purely freshwater fishes. But while 

 these were evolving into varied genera, two allied divisions, 

 the Platysomidae and Catopteridae were diverging from 

 them, at the same time that they often continued to inhabit 

 the same lakes and rivers. The Platysomidae is made up 

 of the genera Eurynotus, JVardichthys, Cheirodopsis, Platy- 

 somiis, Mesolepis, Cheirodus^ and Glohulodiis. The first 

 four all make their earliest appearance in Calciferous rocks, 

 and alongside members of the Palaeoniscidae. Thus refer- 

 ence to the list from Eskdale-Liddesdale (p. 318) and to 

 Traquair's list (p. 145) shows all of them. The most 

 persistent of them throughout geologic time was Platysomus 

 that became-very abundant in lakes of the Coal Measures 

 period. There it occurred with Mesolepis (Fig. 46, p. 282) 

 and Cheirodus, but while they died out at the close of that 

 period Platysomus persisted into Permian time. For in 

 the Upper Permian of North England, Germany and Rus- 

 sia, P. gjbhosus or an allied species is found in Marl Slate 

 or in the peculiar lacustrine Kupferschiefer rock, where 

 also the nearly allied Glohulodus occurs. 



As is true of so many other groups of fishes, and even 

 organisms as a whole, steady destruction of all of the 

 Platysomidae as of most of the Palaeoniscidae took place 

 during the Permian, and so the second divergent series from 

 the last-named, or the Catopteridae, first appears in the 

 Triassic. This group, so far as known, is made up of the 

 three genera Catopteriis, Dictyopyge and Perleidus. Re- 

 garding them A. S. Woodward says (/(^p : Introd. VII) : 

 "These fishes possess a palaeoniscid head and shoulder- 

 girdle, while the tail is only hemi-heterocercal, and the 

 single series of supports in the dorsal and anal fins, almost 



