320 SAMUEL W. WILLISTON 



metapodial is but little smaller than the second. The metapodials 

 are all stout, but the digits are short, tapering rapidly. The ungual 

 phalanges are more pointed than in either Limnoscelis or Diadectes; 

 the fifth tarsale, as usual, is small. 



Very slender ventral ribs, for the first time recognized in this 

 genus among the cotylosaurs, are present in numerous specimens. 

 So far as they are preserved, they do not seem to differ from those 

 of Ophiacodon or Varanops, for instance. It is pretty certain that 

 they are absent in the diadectids and Limnoscelis. Why some 

 genera in each order of reptiles should have retained these bones, 

 while others lost them, I am not prepared to hazard a guess. 

 Possibly they have something to do with water habits. 



Fig. q. — Labidosaurus. Life restoration, about one-eighth natural size 



Restoration (Figs. 8 and 9). — The only attempt that has hitherto 

 been made at the restoration of the skeleton of Labidosaurus is that 

 of Broili, which was quite acceptable, considering our little knowl- 

 edge of the genus and its allies at the time he made it. That he 

 placed the front legs so far back as he did, is not surprising; almost 

 anyone would have done likewise at the time ; and in the curvature 

 of the vertebral column he was unduly influenced by the erroneous 

 early restorations of Pareiasaurus, at that time supposed to be a 

 near relative. I may only remark here that the present restoration, 

 based as it is upon so much material, has scarcely anything con- 

 jectural about it, or anything that has not been corroborated by 

 several specimens. As usual, the length of the tail is still in doubt. 

 I have assumed that it was about as long as in the allied captor- 

 hinids, of which we know the tail more definitely. 



Habits. — Granted a fairly complete knowledge of the osseous 

 structure of such early reptiles, there must remain more or less 



