the Ccehicantli Fish. 



325 



uniting by deeply striate sutunil surFaees. The quadrate 

 stands out nearly transversely, but the inner condyle — an 

 almost hemispherical head — lies a little in front of the cylin- 

 droid outer condyle, whose lateral surface is sliglitly concave. 



The meta|)terygoid is a relatively large sheet of bone lying 

 on the outer surface of the pterygoid. Its hinder margin is 

 turned outward and ends dorsally in a process which touches 

 the lower surface of the parietal. The upper border is divided 

 into two concavities by a low elevation in the middle of its 

 length. This general concavity surrounds the process of 

 the sphenoid called basipterygoid by Stensio. In three cases 



Fia-. 3. 



Macropoma mantelli. Left pterygo-qviaclrate apparatus seen from 

 without. X 1. 



Reference-letters as before, with Pal.Th., the tooth-bearing plate 

 attached to the palatine, represented displaced. The epipterv- 

 goid is also slightly twisted backward. 



where I have removed the metapterj^goid in exposing the 

 brain-case, I have satisfied myself that there is no contact 

 between the two elements, which are always separated by a 

 layer of chalk and do not bear a?iy articular facets. 



The anterior end of the metapterygoid is produced into a 

 long process of nearly cylindrical section, whose lower and 

 part of whose adinesian surfaces are supported by a long 

 splint of bone projecting from the upper margin of the 

 pterygoid. 



