HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 295 
Twelfth Dorsal Vertebra. 
Five specimens representing this member of the vertebral series were re- 
covered: No. 1604, No. 1703C, No. 1708, No. 1713, and No. 1715. Specimen 
No. 1604 consists of the centrum, the neural arch, the lower half of the spine, the 
left transverse process, which has been very slightly in- 
jured, and the base of the right transverse process, the 
extremity being lost (see Fig. 57). No. 1703C consists 
of a well-preserved centrum, the neural arch, and the 
lower two-thirds of the spine. The right transverse 
process has been well preserved; the left transverse 
process has been broken off near its end. No. 1708 
is a fragment of the centrum. No. 17138 is complete 
except for the loss of the posterior epiphysis of the 
centrum. Specimen No. 1715 is almost perfect with 
exception of the face for the tubercle of the rib on 
the right side, which has sustained injury; it is also 
slightly waterworn on the articulating faces of the aa 
Fia.57. Twelfth dorsal of M. ela- 
centrum; no injury has been sustained by the spine. 
tus (No. 1604). Xd. 
With the help of the latter specimen Mr. Peterson was 
able to repair the specimen belonging to No. 1604 in such a way as to leave no 
doubt as to the correctness of the restoration. 
The spine of the twelfth dorsal vertebra has about the same height as that 
of the vertebra preceding and succeeding it. Its upper extremity, like that of its 
predecessor, is somewhat bent, giving its upper end a hooked appearance. At 
the tip it is broadened transversely to form ligamentary attachments. In speci- 
men No. 1604 the prezygapophyses look upward and strongly forward; the post- 
zygapophyses look backward and somewhat downward, very slightly inward. 
The transverse process at its extremity is broadened vertically. The mammillary 
process having a sharpened projection which overhangs the prezygapophyses, the 
surface for the tubercle of the rib looks outward and slightly forward. The articu- 
lating faces for the heads of the ribs are widely separated and are relatively smaller 
than in the case of the preceding vertebra. 
MEASUREMENTS OF TWELFTH DoRSAL VERTEBRA.*? 
1604, 1703C, 1708, 1713, 1715, 
mm. mm. mm. mm. mm, 
Greatest height from base of centrum to top of spine.......... 21s Ee Re PUG 154 
Greatest transverse diameter measured across transverse proc- 
ESSES i ie mareireperte Catercia tees ai ehevmec nye eae ert cue a ueien sya 2 117 90 us 118 95 
35 Numbers in italics represent approximate measurements, the specimens being broken or restored. 
