234 FIELD COLUMBIAN MUSEUM. 
MEASUREMENTS OF PRESACRAL VERTEBRZ IN METERS. 


PRESACRAL VERTEBRA. ie: Ti, eae Te V. Vi VII. 










Heéeightgover aut oo er ee .76 .80 . 84 . 86 . 88 .9o .gI 
Breadth across transverse 
DIDCESSEST. cou near ly, Ont 78) eno 
Centrum, length of ...... 427 35 .38 PG .42 .44 43 
Centrum, breadth of pos- 
terior Cnclo ts eer oe PTOT | eT a "36 sare .30. ie 
Centrum, vertical diameter 
aipOstenorcenu anew 726 . 28 IPAS .28 . 26 24 #27 
Centrum, depth of poste- 
rier concavity Wee er. .05 107 .08 .09 .08 .08 .08 
Centrum, length of pleu- 
CAH CIN 4 Aa gl eee -Lo .16 te) me We3 .19 Aide e240 
Centrum, breadth of pleu- 
TANtrumc i's Vl bene weep .07 107 .07 ,06*' | 3 08 .10 .09 
Spine, height above pre- 
ZY SapOphyses.... J. ge. . 26 .29 ied! 33 139 a PAR 
Spine, lateral diameter at 
OTOSt "3 tat ci ee eRe Pri™ | S18 .20 .28 22" 7). a Oem 
Prezygapophyses, breadth 
across articular surfaces | .19 -21 .18 .18 .16 wig a ty 
Prezygapophyses, distance 
between articular sur- 
faces! 4 wesw eee .05 .04 .O4 .04 04 .O4 .O4 
Hyposphene, depth of ar- 
tichlar suxtace ve. .06 .06 .08 .O7 .08 .08 09 

* Modified by distortion. 
** Hstimated. 
SACRUM. 
The sacrum of Brachiosaurus is at once distinguished from that 
of the other large opisthoccelian dinosaurs by its unusual breadth 
across the sacral ribs as compared with its length and the height of 
its component vertebre. (Plate LXXIII.) The specimen under 
consideration has been damaged somewhat by compression, but more 
seriously by later exposure to weathering at the surface. As a 
result, the neural arches of sacrals 11-Iv inclusive were too badly 
damaged to be restored; and with them the centra above the lateral 
cavities. With these exceptions their structure can be determined 
with certainty. 
‘The sacrum is made up of five ilium-supporting vertebre instead 
of four, as originally described,* all of which are firmly codéssified by 
their centra and the distal ends of their sacral ribs. Sacrals 1 to Iv 
are coalesced by their zygapophyses and the base of their diapoph- 
yses, and sacrals 11 and 111 by their spines. As in the typical 
opisthoccelian sacrumt the ribs of sacrals 11, 111, and Iv enter into 
* Am. Jour. Sci.. 4th Ser., vol. 15, p. 303. 
} This publication, Gzo. SEr., vol. ii, No. 4, p. 180. 
