PLATE I 



Described 

 on Page 



Ctenacodon serratus Marsh. i6 



Fig. I. Left lower jaw with P1.4, internal view. X 3 diam. Y.P.M. No. 

 13668. 



Ctenacodon scindens Simpson. 20 



Fig. 2. Part of right lower jaw with P3.4 and M^.,, external view. X 9 

 diam. Type. Y.P.M. No. 10366. 



Ctenacodon sp. 18 



Fig. 3. Ml, crown view. X about 25 diam. Y.P.M. No. 13666. 



Plates I-XXI consist of stereoscopic microphotographs, enlarged from two to 

 twenty-five diameters. They should be viewed either with a stereoscope designed 

 to be placed on a horizontal page or with a stereoscope of the more usual pattern 

 with the projecting arm (designed to carry the postcard-sized stereographs) cut 

 off at two or three inches from the prisms. 



172 



