calcaneum, the latter being without an indication of a prominent heel, although there is a tendency to develop the crurotarsal into the chief joint. The number of vertebrae amounts to eighteen presacrals, eight to ten of which are cervicals. There are two or three sacral and about twenty-four mostly shortened caudal vertebrae. The latter possess intercentral wedges and chevron-bones; wedges occur also between the cervical and some thoracic vertebrae. Some of the posterior cervical ribs are very peculiar–straight, broadened out, turned backwards, partly overlapped by one another, and 18 inches long, recalling the first two ribs of the crocodiles. Sternum and abdominal ribs are unknown. _Elginia mirabilis._–The skull (Fig. 54, A, p. 280)–nothing else is known–indicates one of the most remarkable reptiles hitherto found on this side of the Atlantic. It was discovered in the Red Sandstone of Elgin (Lower Trias). The skull reminds us in its general shape and by its spikes and horns of the little American Iguanoid lizard, _Phrynosoma_. The length of the cranium is about 6 inches, the distance between the tips of the two largest {306}horns measures 9 inches. The teeth are small and resemble those of an _Iguana_ in their shape and finely serrated edges, indicating herbivorous habits, but there are also several rows of smaller teeth on the palate, the configuration of which is not unlike that of _Sphenodon_. The top and sides of the skull, except the interparietal foramen, the orbits, and nostrils, are completely encased by rugose, pitted, dermal bones, most of them with strange, horn-like spikes. In the encasement of the temporal region can be discerned a postfrontal, parietal and squamosal, a conically projecting epiotic, a postorbital and supratemporal, a jugal and a quadrato-jugal, which latter almost completely covers the quadrate bone. The interparietal foramen lies far forwards, almost on a level with the orbits. The nostrils are terminal, surrounded by the short nasals, the maxillaries and the premaxillaries, which latter divide them. ORDER II. THERIODONTIA. The cranium is not roofed in, but shows a pair of large supratemporal fossae, bordered below by the zygoma, which is formed mainly by the squamoso-jugal bridge, and is shut off from the orbit by the postfrontal joining the bridge. The teeth are differentiated into incisors, canines, and molars (Fig. 54, C, p. 280). The lower canines close in front of the upper.