12 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I23 



The frontals are similarly co-ossified, and their maximum width 

 across the posterolateral processes is almost equal to the greatest 

 length of the bone. The pineal foramen pierces the plate just in ad- 

 vance of the parietal border. Low massive olfactory ridges denote a 

 longitudinal groove on the ventral surface. The anteriorly succeeding 

 nasals are large paired elements. Each, in keeping with the forward 



Fig. 5. — Paradipsosauriis mexicaniis, new genus and species (U.S.N.M. 

 No. 20667). A diagram, somewhat restored, of the skull in ventral view. Ap- 

 proximately X 3- 



Abbreviations: a, angular; art, articular; bsp, basipterygoid process; bspr, 

 basioccipital process; occ, occipital condyle; pal, palatine; pt, pterygoid. (Other 

 abbreviations as in fig. 4.) 



opening nostrils, must have possessed a length fully two and a half 

 times their individual widths. The prefrontals are elongate bones 

 with wide contacts with both the nasals and frontals. However, they 

 do not extend far back over the orbits. Anterolaterally, each element 

 displays a low swelling that continues obliquely across the dorsal 

 lamina of the maxillary to the border of the external nares as an 

 indistinct nasolachrymal ridge. The lachrymals are small. Laterally, 

 they are exposed as low, short slivers of bone between the prefrontals 



