200 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



organic environment comprises both the flora and fauna, but in this instance the 

 animals were not, so far as we can see, influenced by the vegetation more than 

 that they profited by the shade of the umbrageous growths, sought refuge in the 

 interstices of submerged roots, or possibly fed upon some forms of the algae in the 

 pool. None of these factors would have left any readable record in the morphol- 

 ogy of the animals. The list of flora occurring in the shales accompanying the 

 coals of the Freeport group has been cited above. 



"The Character of the Contacts within the Fauna. 



"The list of known amphibians from Linton as given by Moodie^ includes 

 51 species. The genera are as follows: 



Brachydectes. Erpetosaurus. Molgophis. Ptyonius. 



Cercariomorphus. Eury thorax. Odonterpeton. Saurerpeton. 



Cocytinus. Hyphasma. CEstocephalus. Sauropleura. 



Ctenerpetom. Ichthycanthus. Pelion. Stegops. 



Diceratosaurus. Leptophractus. Phlegethontia. Thyrsidium. 



Eoserpeton. Macrerpeton. Pleuroptyx. Tuditanus. 



"If we examine the animals as described and illustrated in Hoodie's excellent 

 monograph, we find that they were, one and all, provided with sharp, conical 

 teeth, suitable only for a carnivorous or an insectivorous diet. This eliminates 

 the vegetation of the period from consideration as a possible source, at least as 

 an immediate source, of food, but introduces a most efi"ective element of stress 

 in the competition between the animals themselves, on the one hand to capture 

 prey and on the other to escape the attack of predatory forms. 



"The possible sources of food were fishes, the amphibia, and very probably 

 the abundant arthropods, molluscs, and insects, though practically no traces of 

 invertebrates have been found with the remains of the amphibians, except the 

 casts of spirorbis-like forms. While there can be little doubt that some of the 

 amphibians were carrion-eaters and scavengers, the ultimate food-supply must 

 have been the invertebrate fauna of the waters and banks, and the very meager- 

 ness of the remains of such a fauna speaks eloquently of the crowded habitat 

 and the eager search for every edible particle. Beyond this the diet was of flesh 

 and the fauna was self-devouring. 



"From the description given it seems fairly certain that the amphibian fauna 

 was isolated in a pool of clear water surrounded by a great stretch of swamp. 

 The ordinary factors of environment which influenced the development of a 

 fauna were absent or ineffective, the physiography and the climate were monot- 

 onous in the extreme; the vegetation had only an indirect effect. The main stress 

 upon the life was competition within the fauna. This stress became very high 

 with the crowding of the pool, but as the monotonous environment afforded 

 but limited possibilities for the formation of new habits, adoption of new habitats 

 or the assumption of a new group of contacts in any form, it was not relieved by 

 any overspecialization either in structure or habit. A study of the amphibia 

 reveals only a very normal group of animals. They varied in size from 10 feet 

 to 6 inches in length, some were squat and sluggish, others lithe and serpentiform, 

 some even so snake-like that they had lost their limbs. Some hid for safety in 

 dark holes and corners, others lurked in the slime, feeding on carrion or the less- 

 active and well-protected forms; still others flashed through the water in active 

 pursuit of prey and dared give battle in their conscious strength. It was a 



1 Moodie, Roy L., Carnegie Inst. Wash. Pub. 238, p. 18, 1916. 



