28o Evolution and Distribution of Fishes 



Marine. 



Carcharopsis prototypus 

 Cladodus milleri 

 Cladodus mirabilis 

 Cladodus striatus 

 Cochliodus (Deltoptychius) 

 Cochliodiis acutus 

 Cochliodus compactus 

 Cochliodus contortus 

 Cochliodus magniis 

 Cochliodus (Xystrodus) striatus 

 Deltoptychius acutus 

 Ctenoptychius dentatus 

 Homacanthus microdus 

 Glossodus marginatus 

 Helodus denticulatus 

 Helodus didymus 

 Helodus mammillaris 

 Oracanthus milleri 



Oracanthus minor 

 Orodus cinctus 

 Petrodus patelliformsi 

 Petalodus hastingsiae 

 Petalodus lobatus 

 Petalodus (Petalorhynchus) 



benniei 

 Petalodus (Petalorhynchus) 



psittacinus 

 Paecilodus aliformis 

 Paecilodiis jonesii 

 Polyrhizodus pusillus 

 Polyrhizodus radicans 

 Psammodus porosus 

 Psammodus rugosus 

 Psephodus magnus 

 Physonemus sp. 



In further explanation of the writer's classification of 

 Young's list he would add that this was prepared by separat- 

 ing all those that were invariably reported from marine 

 limestones, such as the North Mine, Kirkton, Peter's Hill, 

 Broadstone, Dockra, Roughwood, Calderside, and New- 

 field from other deposits of freshwater origin like Ruther- 

 glen, New Mains, Carmylie, Barkip, etc., in which all of 

 the fish remains lie side by side with carboniferous plants, 

 Estheria^ and labyrinthodont remains. The conclusion to 

 be drawn is that during late Devonian or early Calciferous 

 times an extensive migration of elasmohranch and chima- 

 eroid fishes occurred from the lakes, swamps, and fivers, 

 into the shore margins and seas of those times. In the 

 process, and doubtless due in no small measure to changed 

 environment of waters, food, or defence and offence, as 

 well as other agents, many new species and in time genera 

 evolved there, as the list of Davis in particular strongly 

 suggests. Alike the Hybodontidae, the Orodontidae, the 

 Cochliodontidae, the specialized Psammodontidae and the 

 Petalodontidae seem all to have participated in the move- 

 ment seaward, while so far as present information goes 

 the Psammodontidae evolved as a purely marine derivative 

 group, from a still more ancient stock of anadromous, and 

 before that of freshwater ancestry. 



From the Lower Carboniferous upward even to the 

 Permian in some cases, the large group of the Petalodonti- 



