Some Additional Characters of the iMosasaurs. 



Contribution from the Paleontolog^ical Laboratory, No. 42. 



HV S. W. WILLIS TON. 



With Plato XII. 



In the last numlier of this Quarterly there was a brief note con- 

 cerning some interesting new features of Platccarpiis, as derived 

 from a remarkably perfect specimen collected the past summer in 

 Gove count}', Kansas. With the present communication is given a 

 photographic illustration of the nuchal fringe, there briefly de- 

 scribed. Tlie fringe in the specimen fortunately lies slightly 

 displaced from the vertebral column in the neck, so that it is visible 

 as far back as the scapula of the right side, beneath which it 

 disappears. The length of each individual "thong" cannot be 

 made out. since they are more or less entangled, but they seem to 

 be four or five inches long. They are numerous, starting in a close 

 row and lying loosely on each side. I am not able to compare 

 them with the dorsal projections of any of the recent lizards in 

 which similar structures occur, but certainly the striking fact that 

 such appendages do occur in this genus of the Mosasaurs, at least, 

 adds another argument to prove the close relationship of the 

 Mosasaurs with the lizards. The thongs were evidently nearly 

 round in cross-section, and loose and pendulous, not standing up 

 rigidly The foremost ones are found in the specimen lying be- 

 neath the angle of the mandible, so that it is evident the fringe 

 began at the posterior part of the head. How far l:)ackward it 

 reaches can not be. said without removing the bones beneath which 

 they disappear. In all probability it continues well back along 

 the dorsal region, possibly on the tail. 



The last cervical ribs are shown in part in the illustration. The 

 first thoracic rib, attached to the eighth post-cranial vertebra, has a 

 length of over 300 millimeters; its distal end is covered so that its 

 precise length can not be made out. The last cervical rib has a 



(30) KAN. UNIV. QUAR,, VOL. VIII, NO. 1. .IAN.. 1899, SERIES A. 



