4. Deinodon horridus, Leidy. This genus and species are founded on a number of specimens, consisting of fragments of teeth of a saurian reptile, discovered by Dr. Hayden. Nine of the specimens referred to consist of crowns of teeth or of their summits, which resemble those of Megalosaurus, being compressed conical and curved, and having trenchant, dentated borders. They are generally thicker in relation to their breadth than in Megalosaurus, which might only be a specific distinction, were it not that there are several other teeth in the same collection apparently of the same animal, but quite peculiar in form. One of the specimens is a curved conical crown, nearly circular in transverse section, having a prominent dentated ridge on ea...