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:--