No. I.] THE SKULL LV THE MOSASAURID^. 13 



paroccipital, squamosal. Above, it reaches the descending 

 processes of the parietal. 



The Parietals (Fig. 8). 



The parietals are completely co-ossified. They are more con- 

 stricted in the middle than in the Varanidae, and the descending 

 processes are not so broad, but extend farther down, to join the 

 petrosal and epipterygoid. The long posterior processes join 

 the squamosal. There is a peculiar upper portion of the parie- 

 tal ; it is triangular behind, and its conditions are better seen 

 in the figure than they can be described. The front portion of 

 the bone is insected by the pineal foramen. The parietal has 

 the following connections : below, supraoccipital and petrosal ; 

 behind, squamosal and quadrat ojugal (very little) ; laterally, 

 postfrontal; in front, frontal. The sutures between the two 

 latter elements are very deeply cut, and the elements very 

 strong in this region. The parietals never reach the basi- 

 sphenoid, and there is no ossified alisphenoid, as stated by Pro- 

 fessor Cope. 



The Frontals (Figs. 6, 7). 



These bones resemble very much the elements in Varanus. 

 They are co-ossified, but a division is visible in front, extending 

 between the long anterior processes. The frontals form a 

 shield-like element, ending in two long separate processes in 

 front ; there is an incision behind for the pineal foramen, which 

 in this genus is placed between frontals and parietals. On the 

 sides, they are bent out to meet the prefrontals. Besides the 

 two long median processes in front, there are two other ones, 

 one on each side, which, exactly as in Varanus, form the pos- 

 terior end of the nasal openings. A sharp ridge runs in the 

 middle line of the frontal above, but disappears behind. The 

 olfactory lobe is placed in a deep groove on the lower side of 

 the frontal ; this groove is well developed in the middle, but 

 vanishes in front. The shape of the frontal is easily seen in the 

 figures. The frontals have the following connections : behind, 

 parietals; laterally, postfrontal, prefrontal; anteriorly, naso- 

 premaxillaries. The naso-premaxillaries overlap the long ante- 

 rior processes of the frontals, and extend a little more behind 

 than the nasal openings. 



