6J8 GEOLOGY* 



have been found, showing that gills were possessed in the early stages, 

 that they were lost later, and that finally the adult amphibian form 

 was assumed, thus establishing fully the amphibian metamorphism. 

 The ventral surface was usually protected by small overlapping plates 

 or scutes, and these sometimes extended to the legs and back. Two 

 genera (from Linton, Ohio) have been referred to this suborder, per- 

 haps with some doubt. Other genera are known from the Permian of 

 Bohemia, Saxony, and France. 



The Aistopoda were snake-like forms whose limbs had been atro- 

 phied, which implies that a degenerative development had already 

 taken place. The elongation of their bodies involved a notable multi- 

 plication of the vertebrae, one form having no less than 150, The 

 animals, or some of them, were protected by scutes beneath, and were 

 armed with small ossicles on the back. Their teeth were simple hollow 

 cones without infolding. Two genera (Phlegethontia and Molgophis) 

 have been found in Ohio, one or two in the Carboniferous of Ireland, 

 and two in the Lower Permian of Bohemia. One of the Irish genera 

 (Dolichosoma) is very closely related to the Ohio forms, and they have 

 even been supposed to be identical, a significant fact in view of their 

 wide separation and their limited means of dispersion. 



The Microsauria were like the branchiosaurs in having salaman- 

 drine forms, and conical teeth with simple or only slightly infolded 

 walls. Compared with the other suborders, their vertebrae were 

 more like those of the modern reptiles, their skeletons were more com- 

 pletely ossified, their skulls contained less cartilage, and their limbs 

 were longer and stronger. Some of them at least probably ran with 

 lizard-like agility, and perhaps climbed readily, since many have been 

 found in the trunks and stumps of trees, as in the coal-mines of South 

 Joggins, Nova Scotia. A score or more of genera, often imperfectly 

 known, are referred to this suborder from the Carboniferous of 

 America (Nova Scotia and Ohio), and from the Carboniferous (Ireland, 

 Figo 282) and the Lower Permian (Bohemia and Saxony) of Europe. 

 They were in some respects highly differentiated, and are regarded by 

 some paleontologists as the ancestors of some or all the reptiles. 



The true labyrinthodonts were doubtless the largest and most 

 characteristic amphibians of the period, though yet imperfectly known. 

 They take their name from the form of the dentine of their teeth, which 

 was usually intricately infolded, giving to the cross-section a beautiful 



