206 HISTORICAL PALEONTOLOGY. 



mian rocks to which of these formations the beds containing 

 them should be referred; but it is obvious that this method 

 of procedure is seriously liable to lead to error. In accor- 

 dance, however, with this, the only available mode of deter- 

 mination in some cases, the remains of Thecodontosaurus and 

 Palaosaurus discovered in the dolomitic conglomerates near 

 Bristol will be considered as Triassic, thus leaving Protoro- 

 saurus * as the principal and most important representative of 

 the Permian Reptiles, f The type-species of the genus Pro- 

 torosaurns is the P. Speneri (fig. 138) of the "' Kupfer-schiefer " of 

 Thuringia, but other allied species have been detected in the 

 Middle Permian of Germany and the north of England. This 

 Reptile attained a length of from three to four feet ; and it has 

 been generally referred to the group of the Lizards ( Lac ert ilia}, 

 to which it is most nearly allied in its general structure, at the 

 same time that it differs from all existing members of this group 

 in the fact that its numerous conical and pointed teeth were 

 implanted in distinct sockets in the jaws this being a Croco- 

 dilian character. In other respects, however, Protorosaurus 

 approximates closely to the living Monitors (Varanida} ; and 

 the fact that the bodies of the vertebrae are slightly cupped or 

 hollowed out at the ends would lead to the belief that the 

 animal was aquatic in its habits. At the same time, the 

 structure of the hind-limbs and their bony supports proves 

 clearly that it must have also possessed the power of progres- 

 sion upon the land. Various other Reptilian bones have been 

 described from the Permian formation, of which some are prob- 

 ably really referable to Labyrinthodonts, whilst others are 

 regarded by Professor Owen as referable to the order of the 

 " Theriodonts, " in which the teeth are implanted in sockets, 

 and resemble those of carnivorous quadrupeds in consisting 

 of three groups in each jaw (namely, incisors, canines, and 

 molars). Lastly, in red sandstones of Permian age in Dum- 

 friesshire have been discovered the tracks of what would ap- 



* Though commonly spelt as above, it is probable that the name of 

 this Lizard was really intended to have been Proterosaurus from the Greek 

 prof eras, first ; and saura, lizard : and this spelling is followed by many 

 writers. 



t In ah extremely able paper upon the subject (Quart. Journ. Geol. 

 Soc., vol. xxvi.), Mr. Etheridge has shown that there are good physical 

 grounds for regarding the dolomitic conglomerate of Bristol as of Triassic 

 age, and as probably corresponding in time with the Muschelkalk of the 

 Continent. 



