HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 291 
Horizontal diameter of posterior face for head of rib................... 20 17 20 
Antero-posterior diameter of face for tubercle of rib.................... 25 17 
Transverse diameter of face for tubercle of rib........................ 22 16 
Mransverseviameten Of pedicelumin, satan ctiete see csaee dine oo ae seo 33 23 27 
Antero-posterior diameter of pedicel..............-.5.-2----0--+- eee 35 28 33 
Distance between faces for head of ribs................-------+-++--- 26 25 24 
Height of spine from neural canal to extremity.....................-.- 168 . OY 
Antero-posterior diameter of spine above neural canal.................. 40 32 
Antero-posterior diameter of spine at top below tubercle................ 30 24 
The Tenth Dorsal Vertebra. 
Three specimens representing the tenth dorsal were recovered, No. 1604, 
No. 1713, and the centrum of No. 1731. No. 1604 preserves a considerable portion 
of the centrum, though greatly injured on the anterior face, which has been restored. 
The entire neural arch, the right transverse process, and the spine are well pre- 
served in this specimen. The extremity of the left transverse process was broken 
and has been restored to conform to the process on the right, which is well pre- 
served. In specimen No. 1713 the bone is quite com- 
plete, lacking only the posterior epiphysis of the centrum 
and the articulating face for the tubercle of the rib on 
the left side. Specimen No. 1718 is evidently that of an 
immature animal somewhat smaller than specimen No. 
1604. There is considerable difference in the form of the 
upper end of the spine. The tubercular thickening at the 
extremity of the spine is not nearly so massive, though 
quite as broad, as in specimen No. 1604. The centrum 
of specimen No. 1731 is well preserved, though the articu- 
lating surfaces for the heads of the rib have sustained 
considerable damage. The prezygapophyses are preserved ZA =s 
in position in this specimen and enough of the neural sone See Aa at Me 
arch to indicate approximately the correct measurements; elatus (No. 1604). 3. 
the transverse processes and the spine are lost. 
The length of the spine in the tenth dorsal is very nearly the same as in the 
preceding and succeeding dorsals. At the upper extremity it is rugose and greatly 
thickened for ligamentary attachments. In specimen No. 1604 the upper ex- 
tremity of the spine is deeply excavated like the ninth dorsal in the same specimen 
and the upper extremity is somewhat falcate in outline. This backward curving 
of the superior half of the spine is not seen in specimen No. 1713. The prezyga- 
pophyses in No. 1604 look upward, strongly forward, and slightly outward. They 
