PERMIAN PERIOD 65 



These fishes were doubtless the most highly developed of 

 Permian forms, and were the forerunners of great develop- 

 ments in fish-life. As yet they were small in size, and 

 insignificant in number. 



Meanwhile the other flexibly finned ganoids, with more 

 gristly skeletons, harder scales, and old-fashioned tails, were 

 greatly on the increase, being represented by old and new 

 genera (Platysomus, Palceoniscus, Amblypterus). 



The fringe-finned ganoids were still losing ground. But CROSSOP- 

 if, as seems likely, their Order had been more or less bound TERYGIAN 

 up with the evolution of amphibians, they were not sinking GANOIDS 

 into obscurity with dishonour. 



Many old genera of fishes of the lung-breathing type had now DIPNOANS 

 disappeared ; and only two or three new genera made their 

 appearance (Conchopoma, Sagenodus). This division of fish- 

 life had certainly lost importance, in spite of its double- 

 breathing abilities. 



Nor do the sharks seem to have been enjoying much SHARKS 

 prosperity. Possibly such as subsisted on finny life had been 

 handicapped by the increased speed and wariness of their 

 prey. Some forms, however, that had appeared in the 

 Devonian, and had descendants with better-developed breast- 

 fins in the Carboniferous, were now represented by species 

 still better off in that respect (Acanthodes). But it cannot 

 be said that sharks were holding any remarkable sway in 

 the seas. They were, no doubt, the best brained of all the 

 fishes ; and sharks, indeed, enjoy this pre-eminence at the 

 present time. 



The marine invertebrate life, so far as it is known, presents 

 few distinctive features from that of the last Period. There 

 is certainly not much progress to report in its fortunes. 

 Indeed, for the most part, it seems to have been in a greatly 

 depressed condition. The plight of some of its Orders is 

 intelligible enough, for signs of decay had long been in 

 evidence : but other groups that had been more or less 

 prosperous, and are known, moreover, to have fared well in 

 later Periods, seem for the time to have been wellnigh in 

 extremis. Not only do they appear to have diminished in PROTOZOANS, 

 numbers, but to have been reduced also in size. Even the ETC. 



