106 University of Kansas Geological Survey. 



Maxillae. 



Clidastes velox. The maxillae have fifteen or sixteen teeth, 

 the last one in the latter case small. The inner side has a strong 

 longitudinal ridge, emarginate anteriorly, for the anterior pala- 

 tine foramen, with a groove or cavity above it, arched over by 

 the flattened upper part of the bone. The borders for union with 

 the premaxillse, back of the vertical part, are nearly parallel to 

 each other in the skull. The narial openings are elongated and 

 narrow, the maxillary border thin, with a deep emargination 

 in front. Posteriorly here is a small, flattened process overlap- 

 ping the prefrontal on the upper surface of the skull. The pos- 

 terior end terminates in a slender, pointed projection, partly 

 covered over above by the jugal. On the outer side there are 

 fifteen dental foramina above the teeth, and some smaller ones 

 anteriorly. The bone articulates with the premaxilla, vomer 

 (turbinate?) , palatine, prefrontal, jugal, and lachrymal. The 

 border for the palatine is thinned, beveled, and roughened, ex- 

 tending as far forward as the fourth tooth from the end. The 

 border for the jugal is straight and thin, reaching as far for- 

 ward as the antepenultimate tooth. Below this border on the 

 inner side there is a narrow and deep excavation. The articular 

 surface for the vomer is short and small, very near the anterior 

 end of the bone, on the front extremity of the inner ridge and 

 above the first two teeth. Just above this surface posteriorly 

 there is a small, smooth depression. 



The maxilke of Mosasavrus horridus have fourteen teeth. The 

 bone is narrower than in Clidastes. The beginning of the nares 

 is opposite the sixth tooth. The nares are much elongate, 

 reaching beyond the posterior end of the nasals. 



Platecarpus. PI. xxv, ff. 1, 2. The maxillae are stouter and 

 shorter than in Clidastes. The border for the articulation with 

 the premaxilla^ runs nearly straight and oblicpuely to an ob- 

 tusely rounded point, which is separated by only a short space 

 from the one of the opposite side, just before the beginning of 

 the nares. The free border back of this is thickened, rounded, 

 and deeply emarginate anteriorly. From the posterior end of 



