WII.LISTON: NEW OR LITTLP: KNOWN EXTINCT VERTEBRATES. 167 



7naxi- 

 horndiis. ,„jiif,ni. 

 nun. mm. 



Length from tip of rostrum to occipital condyle 880. . 



Total length of lower jaw loio. . 



Width of cranium through posiurbilal pruccssscs 360 . . 240 



Length from anterior end of the nares to the occipital 



condyle 690. . 540 



Length of narcs 230 . . 170 



Greatest width of frontal bunc 240. . 168 



Length of dentigerous border of mandible 500 . . 



Length from end of articular to anterior end uf the 



coronoid 340 ■ • 205 



Width of mandible tliruugh uiiddie ut coronoid 130. . 85 



There are fifteen teeth in the mandibles, and si.\teen in the u] per 

 jaw, two of which, on each side, are in the premaxillary. They 

 show facets, as figured for Af. inaxii)iiliaiii. A marked peculiarity of 

 the present specimen is the structure of the outer end of the 

 ectopterygoid i)rocess. It has a vertical face, directed outward and 

 abutting against the coronoid; it shows no trace for union with a 

 transverse bone. The face is slightly concave vertically, and 

 flattened antero-posteriorly, measuring in the former direction, 65 

 millimeters, in the latter 25. 



The hypopophyses of the cervical vertebrae are free, and the 

 chevrons of the caudals are firmly united. There are rudimentary 

 zygosphenes on the anterior vertebrae. In the hopes of rendering 

 the coracoid and scapula more complete, I have not figured them. 

 The coracoid is apparently not emarginate, and both bones resemble 

 those of Clidastrs. The parts found in apposition are figured in 

 plate XVL The front jjaddle of the typical species of Mosasaurus, 

 notwithstanding that the genus has been known for so long, is yet 

 unknown. Dollo says: " Les os du carpe (]ue nous possedions et 

 une nageoire anterieure quasi-entiere nouvellement entree montrent 

 de telles analogies entre Mi'sastvt/-/fs et Ciidastes qu'il parait certain 

 que les membres de devant du premier etaieut, aussi, functionellement 

 pentadactyles. "* There is no longer doubt of the pentadactyle char- 

 acter of the front feet oi Mosasai/rus, if the present species belongs to 

 that genus. Dollo has shown (I. c. ) on the other hand that Mosasau- 

 rus has but four digits in the hind paddle, and in all probability our 

 species will prove to have the same number. One will await with interest 

 the publication of the distinguished Belgian anatomist's researches 

 upon the front paddle of Mosasaurus. By examination of the plate 

 herewith given the striking similarity of the front paddle of Clidastt's 

 and Mosasatii-tis will be evident. This similarity is of the more 

 interest because of the fact that both genera show the highest degree 



♦Bull Soc. Belg. de Geol. iv, 349. 1894. 



