168 PALEONTOLOGY 



impressions of the hind feet are but little in the rear of the 

 fore feet. With these footmarks were associated shrinkage 

 cracks, such as are caused by the sun's heat upon mud, and 

 rain-drop pittings, with the signs of the trickling of water on 

 a wet beach, — all confirming the conclusions derived from the 

 footprints, that the quadrupeds belonged to air-breathers, and 

 not to a class of animals living in and breathing water. 



Class II.— REPTILIA. 

 Order I.— Gangcephala.* 



The name of this order has reference to the sculptured and 

 externally polished or " ganoid " bony plates with which 

 the entire head was defended. These plates include the 

 "post-orbital" and "super-temporal" ones, which roof 

 over the temporal fossae. There are no occipital con- 

 dyles. The teeth have converging inflected folds of 

 cement at their basal half. The notochord is persistent ; 

 the vertebral arches and peripheral elements are ossified ; 

 the pleurapophyses are short and straight. There are 

 pectoral and pelvic limbs, which are natatory and very 

 small ; large median and lateral " throat-plates ;" scales 

 small, narrow, sub-ganoid ; traces of branchial arches. 

 The above combination of characters gives the value of 

 an ordinal group in the cold-blooded Vertebrata. 



Genus Apateon, Von M. ; ARCHEGOSAURUS,t Goldf. 



The extinct animals which manifest the above ordinal 

 characters were first indicated by certain fossils, discovered in 

 the sphecrosideritic clay-slate forming the upper member of the 

 Bavarian coal measures ; and also in splitting spheroidal con- 

 cretions from the coal-field of Saarsbruck, near Treves. They 

 were originally referred to the class of fishes (Pygoptcrus Lvcin*, 

 Agassiz) : but a specimen from the Brandschiefer of Miinster- 



* Tavos, lustre; KcpaXn, head. 

 f hiraTiwv, a cheat; apx^yos, beginning; aavpos, lizard. 



