_Rhynchosaurus_ from the Upper Trias of Warwickshire and Shropshire, and _Hyperodapedon_ of the same age, found at Elgin, in Warwickshire, and also in Central India, are rather large, _H. gordoni_ measuring 6 feet in length. Both have a short, broad, and stout cranium, and curved down, toothless premaxillae, hence the name Rhynchocephali; the nares are confluent; the teeth are numerous and small, and are liable to be worn down so that the animals ultimately bite with the edges of the jaws, to which the teeth are ankylosed. The premaxillaries of _Rhynchosaurus_ are curved downwards over a slightly upcurved, likewise toothless process of the mandibles, which form a strong symphysis. All the teeth are very small, absent, or minute on the mandibles, forming one series on the maxillae, several rows on the vomers and especially on the palatines, which latter remain separated from each other. _Hyperodapedon_ seems to have lost the intercentra; its vertebrae are solid, those of the neck are opisthocoelous. The interparietal foramen is likewise abolished. The hook-shaped end of the curved-down premaxillae fits into a bifurcation of the mandibles in front of their stout symphysis. The teeth are similar to those of the other genus. Whilst these, the earliest known genera of Rhynchocephali, are already in various ways rather specialised, _e.g._ the hooked beak and the loss of the intercentra, the two following fossil genera, although of much later date, namely Upper Triassic, are more closely allied to the recent _Sphenodon_. _Homoeosaurus pulchellus_ and other species in Germany are only 6 to 8 inches long. The vertebral column consists of twenty-three presacral and many caudal vertebrae. The first five cervicals are devoid of ribs. Intercentra are restricted to the neck and the anterior portion of the tail. The mandibles are not fused together. The nares are divided by a bony septum. Each premaxillary has one rather broad tooth. {293}[Illustration: FIG. 58.–_Sphenodon punctatum._ × ⅓.] {294}The teeth of the maxillaries and mandibles are triangular, much worn down in front. The ribs are devoid of uncinate processes. Closely allied but larger is _Sauranodon_ of France, which has lost the upper teeth and uses the sharp margins of the jaws instead. _Pleurosaurus_ of Germany and France, about 5 feet in length, is remarkable for the shortness of its still pentadactyle extremities, for its short neck, and very long tail;–an interesting parallel to what has happened in many genera of recent lizards. _Sphenodon_ s. _Hatteria_ is the sole surviving member of the whole group of Prosauria, and is represented by one species only, _S. punctatum_, in New Zealand. As the last living witness of bygone ages this primitive, almost ideally generalised type of reptiles, this "living fossil," deserves a detailed description.