Cope,] ^^O [Dec.lg, 



The Liodons with compressed or round dorsal or lumbar vertebrae may 

 be dismissed from comparison. Of the depressed species, L. perlatios, 

 Cope, is known from specimens of one-third or less the size of the present 

 one, which are further peculiar in having the diapophyses of the lumbars 

 to stand on the anterior half only of the centrum. In L. idericits, Cope, 

 the centra are less depressed, and the size still smaller than in the last. 



Among Mosasauri with depressed vertebral centra, it is to be noted 

 that none present so great a degree of depression and lateral extension 

 except the M. hrumbyi of Gibbes. They are all also much smaller. The 

 M. hrumbyi was founded by Dr. Gibbes on two lumbar vertebras from the 

 Cretaceovis of Alabama, which resemble those of the if. dyspelor in form, 

 and also in size. It is probably its nearest ally, and may be a Liodon. 

 Dr. Gibbes established the genus Amphorostens for it, but without suf- 

 ficient evidence to support it. The principal point of distinction between 

 it and the L. dyspelor which I observe is the lack in the former of the 

 strong emargination of the superior margin of the articular surface for 

 the floor of the neural canal, which is so marked in the latter. I have 

 only the figures of Gibbes to rely on for this particular, and it is scarcely 

 probable that the artist would have overlooked it had it existed. Should 

 the bounding prominences have been worn off, then the restored centrum 

 would have had a notably greater vertical diameter than in the L. dyspelor 

 in the same portions of the vertebral column. As a second character, I 

 note that, relying as before on Gibbes' figures, the external angles of the 

 depressed bal] are not so extended laterally in M. hrumbyi. 



In size the vertebrte of the present animal exceed those of the M. 

 hrumbyi. The latter has been hitherto the largest known species of the 

 order Pythonomorpha, exceeding two-fold in its measurements the M. 

 giganteus of Belgium. So the present saurian is tAvice as great in dimen- 

 sions as the New Jersey species I have called M. maxi7mis. If, as appears 

 certain, the M. missuriensis discovered by Webb measures seventy-five 

 feet in length, the 3L maximus measured eighty, and the 31. dyspelor 

 could not have been less than one hundred feet in length. This is much 

 the largest reptile known, and approaches very nearly the extreme of the 

 Mammalian growth seen in the whales, though of course without their 

 bulk. Such monsters may well excite our surprise as well as our curiosity 

 in the inquiry as to their source of food supply, and what the character 

 of those cotemporary animals preserved in the same geologic horizon. 



The locality whence this reptile was procured is near Fort McRae, in 

 New Mexico. It was discovered by Dr. W. B. Lyon, surgeon at that 

 post, and by him sent to the Army Medical Museum at Washington, 

 whose director placed it in the collection of the Smithsonian Institution. 

 The attention to the palaeontology of his neighborhood by Dr. Lyon will 

 always be cause of satisfaction to students, and his name will be remem- 

 bered with that of Turner (discoverer of the Elasmosaurus platyurus, 

 Cope), Sternberg, and others. 



The stratum is the yellow chalk of the upper cretaceous, which has 

 yielded the L. ictericus, L. proriger, Polycoiylus, etc., in Kansas, and of 



