160 Transactions. — Zoology. 



axially as ridges on to the post-zygapophyses, and from No. 8 

 to 16 the spine cannot be distinguished from the ridge. But 

 in No. 17 the spines again appear, increase in size on each 

 posterior vertebra, and coalesce into a single spine on No. 21. 

 In these vertebrae a distinct hyperapophysis can be recog- 

 nized on the post-zygapophyses. This remarkable blending of 

 the neural spines, hyperapophyses, and post-zygapophyses 

 into two longitudinal ridges is very characteristic of the 

 Dinornithidse, and enables the cervical vertebras to be dis- 

 tinguished from those of all other birds. Sir R. Owen and 

 Professor Mivart call them the hyperapophyses, and Mr. 

 Lydekker calls them the post-zygapophysial ridges. They 

 will be distinguished in the present paper as the neural ridges. 

 Between the pre-axial ends of the neural ridges there is a 

 transverse bony bar, considered by Lydekker as the neural 

 spine, on the post- axial side of which there is a deep fossa for 

 the ligament. This transverse bar increases in height on the 

 posterior vertebrae until it becomes blended with the neural 

 spines in No. 21. The vertebrarterial canals are larger than 

 the neural canal. 



In the cervico-thoracic vertebras the centra are approxi- 

 mately of the same size in all ; but they can be distinguished 

 by the hypapophysis which in No. 22 forms a compressed 

 central nodule, extending in No. 23 to the pre-axial face, and 

 in No. 24 covering the whole length of the centrum ; usually 

 projecting forwards in front of the pre-axial surface, and getting 

 shallower towards the post-axial surface. 



In the free thoracic vertebrae the centra have all the same 

 length, but increase in breadth from No. 25 to No. 28. In 

 No. 25 the haemapophysis forms a deep keel from the pre-axial 

 to the post - axial articulating surfaces, which is sometimes 

 notched in the centre. In No. 26 the haemapophysis is 

 posterior, but there is also a slight anterior tubercle. In 

 No. 27 the haemapophysis is posterior only, sometimes single, 

 sometimes divided. In No. 28 it forms two widely-separated 

 posterior nodules. No. 27 can generally be further dis- 

 tinguished from No. 26 by the shape of the centrum, which is 

 more compressed in the latter than in the former. 



Of the pelvic vertebrae — Nos. 29 to 44 — No. 30 always has 

 the rib anchylosed to the centrum. Nos. 31 to 33 have 

 transverse processes which unite with the pre-acetabular por- 

 tion of the ilia. No. 34 sends stout transverse processes to 

 meet the proximal ends of the ischia and pubes. In the next 

 three — Nos. 35 to 37 — transverse processes are absent, and 

 this gives rise to a deep fossa on each side, in the centre of the 

 pelvis (the pelvic fossae). Nos. 38 to 44 have transverse pro- 

 cesses which coalesce with the posterior portion of the ilia and 

 form, dorsad, the sacrum, or pelvic disc of Sir R. Owen. 



