318 MEMOIRS OF THE CARNEGIE MUSEUM. 
The First Sacral Vertebra. 
(Plate LIV.) 
The first sacral, in a disarticulated condition, is represented by three speci- 
mens, and the three sacra in which it is found in a codssified state also yield in- 
formation as to its form. The accompanying table of measurements of the different 
specimens shows that there is considerable individual variation. 
MEASUREMENTS OF First SacRAL VERTEBRA.‘7 
1704, 1706, 1713, 1714, 1730, 2102, 
mm mm mm mm mm mm 
Greatest vertical heightiof neuralispines--) sa aa eee ae oeeeeeee 210); 2308 esas Veen anes 
Greatest transverse diameter across ale.................0.00000-- 224 218 210 170 186 218 
Greatest antero-posterior diameter across zygapophyses............ il 12) als 85 no Llao) 
Vertical diameter of anterior face of centrum...................... 50 44 53 80 36 50 
Transverse diameter of anterior face of centrum................... 100 103 103 80 83 105 
Vertical diameter of posterior face of centrum..................... 33 2 47 22 27 35 
Transverse diameter of posterior face of centrum.................. 52 50 72 40 43 65 
lengthror-centrumealongmeuralicanaleae eee ener eine 60 70 55 30. 40 62 
eneth ofcentrumsalonetinterior suriaces oe eee ease aoe ones 65 75 59 40 45 70 
Verticalidiameterofneuralicanalleemsen eee een eee er ere: 26 19 20 15 lt 23 
‘bransversediametenotmeuralucanale semen eee eee ear 42 47 39 40 37 50 
Vertical diameter of prezygapophysial surfaces.................... 32 40 40 28 31 38 
Antero-posterior diameter of prezygapophysial surfaces............. 39 33 27 20 24 32 
Height of mammillary process above prezygapophysial surface...... 10 8 18 8 Pe 
Height of metapophysis above transverse process or ala............ 32 16 55 22 Bi he 
Antero-posterior diameter of metapophysis at origin............... 32 40 32 27 25 40 
Antero-posterior diameter of mammillary process..................- Pal 24 21 16 
Antero-posterior diameter of postzygapophysial surfaces............ ae ae 45 
Transverse diameter of postzygapophysial surfaces................. Be ae 28 
Distance between posterior ends of postzygapophyses and posterior 
face: of Cemtramniy ts ettae ic eee eis d Ok Oo eee 80 ae 45 380 
Antero-posterior diameter of spine above neural canal.............. 44 49 57 29 a 47 
Antero-posterior diameter of spine at extremity................... ce 38 44 
Mengthrotispineraboyemeunalicanal sees ee sen nEeene reer rrte 148s LGs 
The Second Sacral Vertebra. 
We have no knowledge of this element in the sacrum except as it is derived 
from the three sacra in which it exists as one of their codssified components. The 
neural spine in all of the specimens which have been recovered is apparently 
intermediate in its antero-posterior diameter between that of the first and the third 
47 Figures in italics denote approximate measurements, absolute certainty being impossible owing to 
defects. 
