In several instances complete or nearly complete skeletons of mosasaurs have been discovered with the different bones nearly all in the positions and relations they had after the decomposition of the flesh, together with the carbonized remains of the skin and impressions of the investing scales and membranes. The nature of the body covering is therefore known with certainty from nearly all parts of the body. The body everywhere, save on the membrane between the fingers and toes, and perhaps on the top of the skull, was covered with small overlapping scales, very much like those of the monitors. These scales, however, were small and smooth in comparison with the size of the animals, those of a mosasaur twenty feet in length being almost precisely the size of those of a monitor six feet long. The top of the skull seems to have been covered with horny plates, as in most lizards. In one instance parallel dark bars, obliquely placed, and of narrow width, formed by carbonized pigment, were observed by the writer. As has been stated, in some instances fish bones and fish scales have been observed among the fossilized stomach contents, and it is quite certain that the food of these creatures must have been composed chiefly of fishes, though of course it is not improbable that other small vertebrates, birds, pterodactyls, the young of plesiosaurs, and possibly small mammals, may occasionally have formed a part of their diet. That the mosasaurs were very pugnacious in life is conclusively proved by the many mutilations of their bones that have been observed, mutilations received during life and partly or wholly healed at the time of death. Bones of all vertebrates are repaired after injury by the growth of more or less spongy osseous material about the injured part, forming a sort of natural splint. This material is more or less entirely removed by absorption when it is no longer required for the support of the broken ends. Many such injured bones of the mosasaurs have been found; sometimes the bones of the hands and feet have grown together, and not infrequently the vertebrae have been found united by these osseous splints; occasionally even the skull itself, especially the jaws, attest extensive ante-mortem injuries. In a single instance the writer has observed the loss of a part of the tail, where it probably had been bitten off. It may be mentioned, however, that the bones of the tail had no such “breaking points” in the mosasaurs as have those of many land lizards, whereby a part or all may be lost as a result of even a trivial injury, and then regrown. Such a condition in an organ relied upon entirely for propulsion would have been immediately fatal to the existence of the mosasaurs. The large jaws and teeth are in themselves sufficient evidence of the fiercely carnivorous propensities of the mosasaurs. The constant renewal of the sharply pointed teeth, thereby preventing deterioration by use or accident, preserved, even in the