144 



the inner face is more numerously faceted, and striate-grooved. The section 

 at the base is subcircular; higher, the outer face is iiatter, the inner more con- 

 ,vex. The apex is acute, and the cutting-edges strong. 



The frontal is narrow, and differs from the other Platecarpi here de- 

 scribed in having the olfactory groove closed by contraction behind. Both 

 palatines are preserved. They support tw^elve cylindric conic teeth, which 

 have recurved apices and striate enamel. The section of the bone is a flat, 

 transverse oval, where the external transverse process is given off". The shaft 

 of the bone is much expanded inwardly, with a thickened margin ; exteriorly, 

 the margin is thin, and is nearly followed by the series of teeth whose bases 

 are exposed externally, and are therefore pleurodont. The emargination for 



the pterygoid is very deep. 



Measurements. 



M. 



Length of the axis with the odontoid 0.074 



Length of the third cervical 0. 048 



Diameter of the ball of the third cervical, vertical 0. 031 



Diameter of the ball of the third cervical, transverse 0.033 



Elevation of the spine of the third cervical from the centrum 0.046 



Length of the posterior dorsal 0. 068 



Diameter of the centrum, vertical 0.033 



Diameter of the centrum, transverse 0.048 



Length of the basioccipital and basisphenoid 0. 084 



Elevation of the occipital crest above the floor of the foramen magnum 0. 030 



Length of the suapensorium from the foramen ovale 0. 090 



Length of the os quadratum 0. 073 



Width of the distal extremity 0.036 



Length of the os maxillare 0.210 



Depth of the os maxillare at the third tooth 0. 036 



Length of the fourth tooth 0.032 



Length of the crown of the fourth tooth 0. 021 



Length of the pterygoid bone 0. 155 



This fossil was foftnd by the writer projecting from the side of a bluff 

 in a branch of the Fossil Spring Canon, near the mouth of Fox Cafion. The 

 l^luff" was from eighty to one hundred feet in height; and the Platecarpus v/as 

 taken from a position forty feet below the summit, from the yellow chalk. 



Platecarpus ictericus, Cope. 



Characters. — Internal angle of the os quadratum close by the meatus, and 

 continued as a rounded ridge separating the anterior and posterior internal faces 

 of the bone. Median posterior ridge not prominent. Centra of dorsal ver- 

 tebras depressed. Humerus broad, short. 



Description. — This species is represented by portions of a cranium, as post- 



