176 



it will be necessary to consider species referred to Mosasaurus as well as to 

 Liodon, from the fact that some of the former may really be Liodons. The 

 Liodons with compressed or round dorsal or lumbar vertebrae may be dis- 

 missed from comparison. Of the depressed species, L. pcrlatus, 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. 



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. brumbyi of Gibbes. They are all also much smaller. The M. brumbyi 

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

 of Alabama, which resemble those of the M. dyspelor in form, and also in size. 

 It is probably its nearest ally, and may be a Liodon. Dr. Gibbes established 

 the genus Amphorosteus for it, but without sufficient 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's figures, the 

 external angles of the depressed ball are not so extended laterally in M. 

 brumbyi. 



In size, the vertebras of the present animal exceed those of the M. 

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

 order Pylhonomorpha, exceeding twofold in its measurements the M. gigan- 

 teus of Belgium. So the present saurian is much larger in dimensions than 

 the New Jersey species I have called M. maximus. If, as appears certain, 

 the Mosasauroid discovered by Webb measures seventy-five feet in length, 

 and the M. maximus measured eighty, the M. dyspelor must have been the 

 longest reptile known, and approaches very nearly the extreme of the raam- 

 maliau 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 

 contemporary animals preserved in the same geologic horizon. 



