80 



PEOE. H. G, SEELEf ON 



versely on the ventral aspect, while the ventral aspect of this verte- 

 bra is transversely subquadrate, I regard the remains as indicating 

 distinct species, because I have often noticed among Oriiithosaurs 

 that the flattened or rounded ventral condition, as the case may be, 

 in the cervical region also obtains in the sacrum. 



Fig. 1. — Anterior aspect of 

 the vertebra, luhich has 

 lost the jpre-zygapophyses 

 and cervical ribs. 



Fig. 2. — Right lateral aspect 

 of the same specimen. 



SN 



Fig. 3. — Ventral aspect 

 showing the base of the 

 centrum. 



Fig. 4. — Polished vertical sec- 

 tion of the vertebra, showing 

 the chambers in the neural 

 arch and centrum. 



a, articular face of centrum, showing coarse cellular tissue on its slightly worn 

 margin ; p, attachment for the cervical ribs on the centrum ; d, attach- 

 ment for the cervical ribs on the neural arch; n.c, neural canal j pn, 

 pneumatic foramen ; n, cavity in neural arch, and corresponding air- 

 chamber in fig. 4 ; sn, supra-neural air-chamber ; ln, lateral air- 

 chamber in the neural arch ; c, centrum. 



