438 
Gr. J. DE FEJ BR VARY 
intentions migh reach so far, as to eventually rank the « Mosasauridae » 
as a family, with the suborder Platyaota. All this however would seem 
to me an exaggeration, and on my part I should rather be 
inclined not to derive the Mosasauria *s origin from the vicinity of 
Fig. 27. Shoulder girdle of f Tylosaurus dyspleor Cope. (Same specimen as on Text- 
fig. 25.) — Vu nat. size. — Kansas, U. S. A. — From Osborn, op. cit. Fig. 9. 
the phyletic.il stem of Dolichosauromorpha and V aranomorpha, but for biolo¬ 
gical, as well as morphological reasons, I should prefer accepting Osborn’s 
theory 1 that «the Mosasaurs are a very ancient marine offshoot of the 
Lacertilia, retaining certain primitive and generalized Lacertilian charac¬ 
ters and presenting a few resemblances in the skull to the Varanoids ; they 
1 Op. cit. p. 188. 
