maksh.] CLAOSAURUS. 221 



are well shown on PI. LXXII, figs. 1 and 3. On the median line above 

 they meet the narrow extension of the parietals, and exterior to this 

 they form the posterior borders of the supratemporal fossae. In front 

 they unite by a strong process with the posterior branch of the post- 

 frontals. Their posterior border is joined mainly to the exoccipitals. 

 On the outer surface of each squamosal there is a deep pit to receive 

 tbe head of the quadrate, and in front of this a short, narrow process 

 extends down the quadrate, forming a part of the border of the infra- 

 temporal fossa. 



The quadrate bone and its main connections are shown ou PI. LXXII, 

 figs. 1-3. It is firmly supported above by the squamosal, but its dis- 

 tinct, rounded head indicates the possibility of some motion. Ou the 

 outer surface in front it joins by open suture the strong jugal bone, and 

 below this unites with the small, discoid quadratojugal. Its inner 

 margin extends forward into a broad, thin wing for union with tbe 

 pterygoid. The lower extremity is massive, aud moderately expanded 

 transversely for articulation with the lower jaw. 



The jugal is one of the most characteristic parts of the skull, as may 

 be seen from the figures on PI. LXXII. Its main portion is robust, 

 much compressed, and convex externally. On its upper margin it 

 forms the lower border of the orbit and of the infratemporal fossa, 

 sending up a strong process between them, which extends inside aud 

 in front of the postorbital branch of the postfrontal. In front it is 

 strongly united to the maxillary, and above joins by suture with the 

 lachrymal. 



The maxillary bone in Claosaurus is of moderate dimensions, and 

 seen from the outside is overshadowed by the premaxillary and jugal, 

 as shown in the same plate, fig. 1. Its lower dentary border is thickly 

 studded with a regular series of teeth, which slightly overlap those of 

 the lower jaw. From above only a small portiou of the maxillary is 

 visible, as seen in PI. LXXII, tig. 3. 



The lower jaws are long and massive. The predentary bone is robust, 

 aud especially fitted for meeting the strong beak above. The dentary 

 bones are large and powerful, with elevated coronoid processes. The 

 angular and surangular bones are, however, quite short and not espe 

 cially strong. 



THE TEETH. 



The teeth of Claosaurus are confined entirely to the maxillary and 

 dentary bones. In each the teeth are very numerous, and are arranged 

 in vertical series, so that they succeed each other as the functional 

 teeth are worn away. This is seen in PI. LXXVIII, fig. 2, which shows 

 the form of the teeth and their relations to each other in the same 

 series. The number of teeth in each depends upon the position, the 

 series near the middle of the jaw having the greatest number, some- 

 times six or more. The teeth of the upper jaw have the external face 

 of the crown covered with enamel and ridged. In the lower jaw this 



