102 KANSAS UNIVERSITY QUARTERLY. 
The shape of the present paddle seems to be not unlike that of 
Platecarpus. The two larger metatarsal bones are undoubtedly the 
first and fourth, the former in position, the latter displaced proxi- 
mally, while the displaced smaller phalanges must represent the 
fifth toe, which is evidently divaricate, as in P/atecarpus. The fifth 
metatarsal is probably the short, irregular bone lying contiguous 
with the fourth metatarsal. The complete hind paddle of C/dastes 
is not known, but I believe that it is like that of Mosasaurus, and, 
if so, there were but four functional toes, as has been shown by 
Dollo. It is upon this character, together with that of the sternum 
and others, that I have established the two families, Tylosauride 
and Mosasauride, the two typical genera representing the extremes 
of development in this order of reptiles. 
A restoration of Zylosaurus proriger will be given in the next 
number of this journal. 
EXPLANATION OF PLATES. 
Plate IX. Front paddle of Zylosaurus proriger. 
Plate X. Hind paddle of 7y/osaurus proriger. 
Plate XI. Pelvic bones of Zy/osaurus. 
Plate XII. Skin of 7ylosaurus, natural size. 
All the foregoing figures are from the same specimen, collected 
by Prof. F. H. Snow and now in the University Museum. 
we nen ee 
