"Williston.] Mosasaurs. 181 



crops in Colorado. The measurements given by Cope are as 



follows : 



" Length of humerus 100 mm- 



Proximal diameter of same 95 



Distal diameter of same 102 



Length of femur 80 



Proximal diameter of same 65 



Length of a centrum of a dorsal vertebrae without ball 61 



Transverse diameter of cup 60" 



Vertical diameter of cup 53 



Length of a pygal vertebra 55 



Transverse diameter of ball of same 60 



Length of caudal 41 



Depth of ball 52 



Width of ball 52 



"The vertebrae are as much distinguished for their shortness 

 as those of P. latispinis are for their elongation. The articular 

 faces are but little broader than deep, and their planes are 

 slightly oblique. The inferior face is somewhat concave in 

 the longitudinal direction. The zygapophyses are stout, and 

 there are no distinct rudiments of zygosphene. The pygals 

 and anterior caudals have round articular surfaces. One of the 

 latter with strong diapophyses, but posterior, is subpentagonal 

 in outline of cup." 



? Platecarpus latispinis. 



IAodon latispinis Cope, Proc. Amer. Phil. Soc, Dec. 1871. 

 Platecarpus latispinis Cope, Cret. Vert., 156, pi. xxviii, ff. 1-4. 

 ? Platecarpus latispinis Cope, op. cit. 368. 



This species is also from the Fort Pierre, and very doubtfully 

 belongs in this genus. There is not enough of the type speci- 

 men preserved and described by Cope to locate it definitely. It 

 will, however, some time be recognized, I am confident, and for 

 that reason I give Cope's description fully. 



' ' The remains representing this species consist of seven cer- 

 vical and dorsal vertebra? ; five of them being continuous and 

 inclosed in a clay concretion. The type specimens were found 

 by Prof. B. F. Mudge, one mile southwest of Sheridan, near the 

 'Gypsum Buttes.' These display the elongate character seen 

 in IAodon Isevis, etc., but the transverse surfaces are transversely 



