112 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.55. 



Fig. 2. — Cervical and dorsal vertebrae of Triceratops caUcornis Marsh. Type. 

 No. 4928, U.S.N.M. About one-eighth natural size. The second vertebrae 

 from the left is the posterior cervical found in the block of sandstone with the 

 dentaries and is here shown in its proper position in the vertebral series. 



Plate 6. 



Fig. 1. — Right scapula of Triceratops, sp. No. 8013, U.S.N.M. Oblique inter- 

 nal view. Shows the horn-like growth protruding from the inner side of the 

 shaft. 



Fig. 2. — Same as above. Direct internal view. Both figures about one-eighth 

 natural size. 



Plate 7. 



Posterior view of skull of Triceratops, sp. No. 6679, U.S.N.M. About one- 

 eighth natural size. 



D. So., dermosupraoccipital ; Ex. oc, exoccipital ; Q., quadrate ; P., parietal ; 

 B., indicates the upper extent of the parietal where it underlaps the dermo- 

 supraoccipital, at this point the two bones are slightly separated, the inter- 

 vening space being filled by matrix. 



Plate 8. 



Longitudinal section of Triceratops skull through the center of brain case 

 No. 5740, U.S.N.M. About one-eighth natural size. Explanatory drawing of 

 this speciment shown in text figure 1. 



Plate 9. 



Postorbital horn cores of Triceratops elatus Marsh. No. 4708, U.S.N.M, 

 Viewed from the back about one-eighth natural size. This specimen is of 

 interest as showing that the right-horn core was broken off during life, evident 

 from the fact that the stump had healed and rounded over. The size of the 

 horns and other parts belonging to this specimen indicate they belonged to 

 an old individual. 



The specimen known by the field designation as " Sk. 11 " was collected by 

 the late J. B. Hatcher in 1890 from the Lance formation near Buck Creek, 

 Niobrara County, Wyoming. 



