The name Mesosuchia, meaning “middle crocodiles,” by which the ancient members of the Crocodilia have generally been known, was given by Huxley in the belief that they were intermediate between the “true” or modern crocodiles and an ancient group which he united with the order under the name “Parasuchia.” A fuller and better knowledge of the members of this last group has proved very conclusively that they are really less allied to the crocodiles than are some other orders of reptiles, the dinosaurs for instance, and should be properly classed by themselves as a distinct order. And, more recently, it has also become quite apparent that the old crocodiles should not be separated so widely from the modern ones as Huxley proposed; that the differences distinguishing them from the recent members of the order are really not of more than family importance. We thus have left but two chief divisions of the Crocodilia, the Eusuchia and Thalattosuchia; and the latter group even, by some authors, perhaps rightly, are included under the true crocodiles as a family only. [Illustration: FIG. 106.—_Teleosaurus_; skull, from above.] These older crocodiles, the Mesosuchia of Huxley, comprise a considerable number of extinct forms which lived as far back as the early part of the Jurassic, and continued nearly to, if not actually into, Cenozoic time, that is, to the Eocene. They differ from all living forms, chiefly in having, not concavo-convex but biconcave backbones, that is, the more primitive vertebrae with which all reptiles began. Nor was the internal opening of the nasal passages so far back in the mouth as in the later forms. In other respects they did not differ very greatly from some of those now living. All the earliest kinds that we know of—the teleosaurs—had a long, slender snout, resembling very much that of the modern gavials. And they were, for the most part, incased in a more complete bony armor, on both the dorsal and the ventral sides; and the front legs were smaller than those of the gavials even. The resemblance of the living teleosaurs to the modern gavials must have been very great, although the heavier bony armor indicates a less exclusively aquatic life. They probably lived more in the shallow waters of the seas near the shores.