MOSOSAU'RUS, MEUSE LIZARD, a genus of huge marine lizards, whose remains occur in rocks of cretaceous age. Three species are known, one from the upper chalk of Sussex, a second from the cretaceous beds of North America, and the third from the .Maestrielit beds. This last (3f. Hofmann) was first known from a nearly perfect head dug out of St. Peter's Mount in 1780, and popularly called the great of Maas tricht. Originally the property of Hofman, it was taken from him, In virtue of some clause in their charter, by the ecclesiastical authorities of Maestricht. who, in their turn, were compelled to give it up to the victorious French army, and by them it was removed to Paris. It is said that the French cannoniers, when preparing for the siege, had instructions not to point the artillery toward that part of the town in which the precious specimen was deposited. This head is 4 ft. in length, and the animal to which it belonged is estimated to have been 25 ft. long. The total number of the vertebrae was 133:
they were concave in front and convex behind, and were fitted to each other by a ball and-socket joint, admitting of easy and universal flexion; the sacrum seems to have been wanting. The limbs were developed into four large paddles, and these with the com paratively short and strong tail, the bones of which were constructed to give great mus cular power, enabled the animal to move quickly through the water in pursuit of its prey. The jaws were furnished with a single row of strong conical teeth. Cuvier first showed the affinities of the animal. It is most nearly related to the modern monitor, but differs from all modern lizards in its peculiar adaptations for an ocean life, and in its great size. The largest living lacertian is only 5 ft. in length, and of this a large proportion is made up by the tail; the Mososaurus, with its short tail, is estimated to have been at least 25 ft. long.