132 



The postfrontal is large and jirominent, and terminates in the usual 

 posterior process, connecting with the squamosal. 



The prefrontal is a slender, flat, triangular bone. Its orbital portion 

 projects at right angles to the orbital margin of the frontals, and is, in its 

 direction, at right angles to the exterior margin. The latter is in the hori- 

 zontal plane, and is transversely plicate. A strong process projects inwardly 

 from the lower side, and is continued across the latter as a curved, flat-topped 

 ridge, to which the maxillary bone is articulated. It soon reaches the outer 

 margin of the prefrontal. 



The suspensorium is flat (perhaps on account of pressure). Tlie opis- 

 thotic sends a flat process to the parietal. The squamosal is, as usual, a 

 sickle-shaped bone, with a flat extremity for articulation with the opisthotic. 

 Unlike what is observed in Platecarpus and Mosasmirns, it presents no concave 

 articular face below for the articulation (by ginglymus) of the quadrate. 

 The exoccipital extends to near the end of the suspensorium, and terminates 

 in a flat extremity with truncate border. The proiitic, on the other hand, 

 terminates near the middle of the length of the suspensorium by a transverse 

 suture. The basis cranii I have not yet found among the debris of this 



skeleton. 



Quadrate bone with long internal angle, and rather thick anterior ala, 

 with broad, rugose margin. A prominent, obtuse ridge is continued from the 

 internal angle to the inferior articular extremity; the distal portion being 

 more acute. A rugose process projects at the point where the posterior hook 

 approaches the body, and is continued, as an elevated, narrow ridge, parallel 

 to the one previously mentioned, to the distal articular surface. A button- 

 like knob appears on the posterior margin of the hook opposite the meatal 

 pit. A strong ridge extends, on the outer face of the bone, from opposite the 

 end of the hook to the base of the great ala. The distal articular surface 

 presents two planes : the narrower at the end of the posterior pair of ridges 

 above described ; the larger considerably less distal, like a broad step. 



The maxillary bone descends regularly in front, uniting with the premax- 

 illary by minute suture. Its posterior extremity is slender and acute. The 

 premaxillary is short conic ; not particularly prominent. The palatine bone 

 lias a slight expansion on the inner side ; on the outer, the margin is very 



narrow. 



Tlic teeth number seventeen on the maxillary bones. They are com- 



