144 



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

 at the base is subcircular; higher, the outer face is flatter, 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 twelve 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 

 ire 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 hall of the third cervical, vertical 0. 021 



Diameter of the hall 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. 0G8 



Diameter of tho centrum, vertical 0. 033 



Diameter of the centrum, transverse 0.048 



Length of tho hasioccipital and hasisphenoid 0. 084 



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



Length of the suspensorium from the foramen ovale 0.090 



Length of the os quadratum 0.073 



Width of tho distal extremity 0.036 



Length of the os maxillure 0.210 



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



Length of the fourth tooth 0.032 



Length of tho crown of the fourth tooth * 0.021 



Length of tho pterygoid hone 0.155 



This fossil was found 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 

 bluff was from eighty to one hundred feet in height; and the Platecarpus was 

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



Platecarpus ictericus, Cope. 



Characters. — Internal angle of the os cpiadratum 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- 

 tebrae depressed. Humerus broad, short. 



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



