No. I.] THE SKULL LV THE MOSASAURID^. 15 



to the squamosal, for the reception of the upper head of the 

 quadrate. There is a small process directed towards the parietal 

 processes, to which it is joined. 



The Prefrontal (Fig. 4). 



The prefrontal is a large bone, in which three portions can 

 be distinguished : first, an inner one, which is attached to the 

 frontal as far as the process extends, which forms the posterior 

 end of the nasal openings. From this point it extends far in 

 front, and is overlapped by the posterior process of the maxil- 

 lary, which it receives in a deep groove. The outer anterior 

 part is covered by the maxillary, and the lower portion joins the 

 palate. In all these connections it agrees with the Varanidae. 



The Lachryfnal. 



This small element was not preserved, but it is figured by 

 Goldfuss. 



The Siiperciliare (Fig. i). 



Two bones which I at first considered the ectopterygoids 

 seem to represent the superciliaria. In form they agree with 

 these elements in Varanus. On the prefrontal, where these 

 bones ought to be connected, there is a distinct roughening. 



The Jugal (Fig. 2). 



The jugal is a slender bone, very thin in front, where it joins 

 the upper and outer portion of the lower maxillary process. 

 Posteriorly it is joined to the postorbital ; at this place it is 

 robust and strong, and sends a small process behind, below the 

 junction with the postorbital. Besides the maxillary and post- 

 orbital it joined the ectopterygoid and probably the lachrymal. 



The N'aso-premaxillary (¥\gs. 12, 13, 14). 



The nasals and premaxillaries are completely co-ossified into 

 a single element without trace of suture. This element is only 

 comparable to the corresponding bones in Varanus. The shape 

 is better seen from the figures than it can be described. There 

 is a strong median keel below, extending through the whole 

 length and fitting between the anterior processes of the fron- 



