I. Introduction. Dr. Robert Wiedersheim, of Freiburg-im-Breisgau, has described a remarkably perfect skeleton of a small reptile, which is known as Labyriuthodon Rütimeyeri. The remains are a natural mould of the bones, in friable sandstone contained in two slabs, so divided as to display in many cases the under and upper surfaces of the cavities from which the bones have been dissolved away. The fossil was found at Riehen, near Basel, in the Bunter Sandstone ; and is preserved in the Museum of the University of Basel. Prof. Wiedersheim made a restoration of the skeleton, which was published in 1878, with figures of both slabs, by the Swiss Palæontological Society. The animal is said to show no trace of abdominal armour, such as characterizes Archægosaurus and most Labyrinthodonts. It does not possess the breast-girdle of median and lateral sculptured bones, found in Labyrinthodonts ; and the skin is inferred to have been naked. The external surface of the skull, which would have demonstrated its form and structure, is not available, having been, as Prof. Wiedersheim states, chipped away to expose the internal mould of the head. The bones are said to have been smooth and free from sculpture ; and on that account the skull is compared to Hylonomus of the Coal Measures. It was regarded us an Amphibian, in opposition to Von Meyer's view that the Labyrinthodontia are true Reptilia.1 The type is unique in Europe. The original figures were unsatisfactory, and I applied to the late Prof. Rütimeyer