The Amphibians of the Permian period belong principally to the order of the Labyrinthodonts, which commenced to be represented in the Carboniferous, and has a large development in the Trias. Under the name, however, of Palœosiren Beinerti, Professor Geinitz has described an Amphibian from the Lower Permian of Germany, which he believes to be most nearly allied to the existing "Mud-eel" (Siren lacertina) of North America, and therefore to be related to the Newts and Salamanders (Urodela).
Finally, we meet in the Permian deposits with the first undoubted remains of true Reptiles. These are distinguished, as a class, from the Amphibians, by the fact that they are air-breathers throughout the whole of their life, and therefore are at no time provided with gills; whilst they are exempt from that metamorphosis which all the Amphibia undergo in early life, consequent upon their transition from an aquatic to a more or less purely aerial mode of respiration. Their skeleton is well ossified; they usually have horny or bony plates, singly or in combination, developed in the skin; and their limbs (when present) are never either in the form of fins or wings, though sometimes capable of acting in either of these capacities, and liable to great modifications of form and structure. Though there can be no doubt whatever as to the occurrence of genuine Reptiles in deposits of unquestionable Permian age, there is still uncertainty as to the precise number of types which may have existed at this period. This uncertainty arises partly from the difficulty of deciding in all cases. whether a given bone be truely Labyrinthodont or Reptilian, but more especially from the confusion which exists at present between the Permian and the overlying Triassic deposits. Thus there are various deposits in different regions which have yielded the remains of Reptiles, and which cannot in the meanwhile be definitely referred either to the Permian series or to the Trias by clear stratigraphical or palæontological evidence. All that can be done in such cases is to be guided by the characters of the Reptiles themselves, and to judge by their affinities to remains from known Triassic or Permian 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 accordance, however, with this, the only available mode of determination in some cases, the remains of Thecodontosaurus and Palæosaurus discovered in the dolomitic conglomerates near Bristol will be considered as Triassic, thus leaving Protorosaurus[20] as the principal and most important
Fig. 138.—Protorosaurus Speneri, Middle Permian, Thuringia, reduced in size. (After Von Meyer.) [Copied from Dana. representative of the Permian Reptiles.[21] The type-species of the genus Protorusaurus 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 (Lacertilia), 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 Crocodilian character. In other respects, however, Protorosaurus approximates closely to the living Monitors (Varanidœ); and the fact that the bodies of the vertebræ 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 progression upon the land. Various other Reptilian bones have been described from the Permian formation, of which some are probably 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 Dumfriesshire have been discovered the tracks of what would appear to have been Chelonians (Tortoises and Turtles); but it would not be safe to accept this conclusion as certain upon the evidence of footprints alone. The Chelichnus Duncani, however, described by Sir William Jardine in his magnificent work on the 'Ichnology of Annandale,' bears a great resemblance to the track of a Turtle.
[Footnote 20: Though commonly spelt as above, it is probable that the name of this Lizard was really intended to have been Proterosaurus—from the Greek proteros, first; and saura, lizard: and this spelling is followed by many writers.]
[Footnote 21: In an 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 dolomitie conglomerate of Bristol as of Triassic age, and as probably corresponding in time with the Muschelkalk of the Continent.]
No remains of Birds or Quadrupeds have hitherto been detected in deposits of Permian age.
LITERATURE.
The following works may be consulted by the student with regard to the Permian formation and its fossils:—