128 University of Kansas Geological Survey. 



pit. The stapedial pit is situated very high up, almost wholly 

 above the meatus, and is more rounded. Its lower border be- 

 hind is low and thin, and forms at the same time the upper 

 margin of the meatal orifice. The suprastapedial process is 

 very stout and broad, descending a little below the middle, and 

 broadly and firmly coossified below with the very large and 

 stout process. Its inner side*is excavated and roughened, with 

 a sharp, thin ridge separating it from the meatus. The poste- 

 rior surface is moderately channeled from side to side in the 

 middle, more deeply so above. The ala seems to have been only 

 moderately broad. Externally the ear cavity is very deep and 

 small, ending in the very large opening inclosed by the supra- 

 stapedial process and the tubercle below. The vertical diame- 

 ter of the rim is only a little greater than the transverse one, 

 and is distinctly less than half the height of the bone, the floor 

 being more nearly horizontal, and not extending nearly so far 

 toward the inferior angle as in all the other quadrates described 

 in the present work. The superior articular surface has a broad 

 and prominent anterior process, with a long concavity between 

 it and the alar process, and a broad upper surface of the supra- 

 stapedial process, which, however, is placed for the most part 

 very obliquely. The outer side, below the ear cavity, is very 

 broad and rugose. The lower articular surface is elongated 

 from side to side, and moderately dilated externally. 



Platecarpus. Pis. lx, lxi. The quadrate of Platecarpus dif- 

 fers very markedly from that of Clidastes in the greatly elon- 

 gated suprastapedial process. On the inner side, the large, 

 oval, stapedial pit is situated higher up. It is larger and more 

 oval, situated nearly as in Brachysaurus ; that is, with its long 

 axis very oblique, its thin posterior border forming the upper 

 margin of the meatal opening. The prominent internal border 

 is formed of a broadly rounded ridge, slightly convex longitudi- 

 nally, ending below in the flattened inner surface of the articu- 

 lation for the pterygoid. Between this ridge and the inferior 

 rugosity there is a shallow pit or channel, very much as in Mosa- 

 saurus. The internal angle above is much less prominent than 



