Many and varied have been the opinions of scientific men regarding the relationships of these animals, as has been intimated. They were thought to be a kind of whale or breathing fish by Peter Camper; crocodiles, by St. Fond; and aquatic lizards, by Adrian Camper and Cuvier. The late Professor Cope thought they were more nearly related to the snakes than to the lizards, and that they might even have been the ancestral stock from which the snakes have descended. Because of this belief he gave to them the name Pythonomorpha, meaning python-like, and this name, really the first ever applied to them, is yet often used instead of Mosasauria. A more complete knowledge of the mosasaurs, however, and especially the recent discoveries of the semiaquatic connecting links, called the aigialosaurs and described on a preceding page, have set at rest all doubt as to their real affinities. They are real lizards, differing less from the living monitor land lizards than do the monitors from some other land lizards, especially the amphisbaenas and chameleons. And to Adrian Camper is due the credit for the recognition of their real relationship, though it required more than a century to prove that he was right. [Illustration: FIG. 80.—_Globidens alabamensis._ Part of mandible, with teeth. (From Gilmore.)] Very recently, and since the foregoing was written, a remarkable new type of mosasaurs has been discovered in Alabama and Europe. Only fragmentary jaws, a few vertebrae, and some skull bones are known, so that it is impossible yet to decide how closely the new form is related to the true mosasaurs, but so far as the evidence goes the only distinguishable character is the teeth. These, instead of being elongated and pointed, are nearly spherical, as shown in Fig. 80. Such teeth could have been used only for crushing shell-fish, and not at all for the seizure and retention of slippery fishes. The genus, which was called _Globidens_ by its discoverer, Mr. Gilmore, includes two known species, from Alabama and Europe, the latter recently described by Dollo. It has been suggested that this peculiar kind of dentition was a more primitive or intermediate one, a kind that the first mosasaurs had before they became fully adapted to the water; but this is doubtful, since _Globidens_ comes from late Cretaceous, and must be one of the later types. If _Globidens_ is a true mosasaur, and it seems to be one, its life-habits must have been remarkably different from those that have long been known. Possibly when the limbs and more of the skull are found, _Globidens_ will prove to be of a distinctive type. SNAKES