OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



49 



Antrodemus (pi. 16), in the American Museum of Natural History, New York, and 



also of Ceratosaurus in the National Museum, to be in error in several particulars. 



Specimen No. 8367, U.S.N.M., has the proximal portions 



of all the cervical ribs of the right side present (see fig. 



18) and a few of the left side. Those of cervicals 4, 5, 



and 6 are firmly anchylosed to the vertebrae. 



The rib of the third cervical of No. 4734 is preserved 



entire and is remarkable on account of its extreme 



slenderness and great length. Its distal fourth bends 



downward, as shown in figure 33, A. From tip to tip it 



measures 268 mm. in length. When articulated, if 



brought straight back along the vertebrae its posterior 



extremity reaches the posterior border of the centrum 



of the fifth cervical. The capitular portion of the rib is 



short and heavy, with an angular, obtuse, roughened 



articular face (fig. 33, B), that unites closely with the 



cupped capitular facet on the vertebra. In aged indivi- 

 duals it doubtless becomes fully coalesced. The tubercular 



process rises from the antero-external side and slightly pos- 

 terior to the capitular process. The articular end is slightly 



expanded, cupped, and fits closely with the outer and under 



side of the diapophyses. On the anterior side and near 



the base of the tubercular process the bone is continued 



forward and downward forming a slender tapering anterior extension that is curved 



in toward the centrum, resembling the cervical ribs of the Sauropod dinosaurs in 



this respect, as in many 

 i A others. On the inner 



side at the base of the 

 tubercular process a 

 small circular opening 

 gives entrance to 

 chambers within the 

 heavier portions of the 

 rib. This opening be- 

 comes larger and more 

 elongate in the pos- 

 terior ribs. The above 

 description of the rib 

 of the third cervical 

 vertebra would apply 

 almost equally as well 

 to the succeeding ribs with the exception that the capitular processes become 

 heavier, the tubercular processes longer and the ribs as a whole more robust. 



Fig. 32.— Anterior chevron of An- 

 trodemus VALENS LEIDY. NO. 8367, 



U.S.N.M. \ nat. size. A, Side 

 view. B, Posterior view. 



Fig. 33. — Cervical rib of the right side of the third cervical, Antrodemus valens 

 Leidy. No. 4734, U.S.N.M. A, J NAT. size. B, head of same, § NAT. size. 



C. CAPITULUM, t, TUBERCULUM. 



