Hutton. — The Axial Skeleton in the Dinomithida. 171 



Thoracic Vertebra. 



The post-axial surfaces of the centra are narrow : in 

 No. 22 the height is rather more than the greatest breadth, 

 and they get narrower to No. 26, in which the height is one 

 and a half times the breadth ; in No. 28 the height is about 

 equal to the breadth in the middle. The anterior pneumatic 

 foramen descends below the rib-facet in No. 28, slightly so in 

 Nos. 27 and 26, and becomes obsolete in No. 24. There is a 

 posterior pneumatic foramen in all. The hypapophysis in 

 No. 22 forms a compressed central nodule, deepest behind. In 

 No. 23 it is longer, but does not reach either end of the 

 centrum. In No. 24 it is continuous as a keel and projects 

 forwards. In No. 25 there is no notch, but a slight posterior 

 nodule, and the keel does not project forward. There is an 

 anterior nodule in No. 26, but not in 27. The transverse 

 processes are rather long and thick; not ascending. The 

 neural spines are long, that of No. 22 sloping forward but 

 slightly, those of the posterior vertebra? often much curved 

 forwards. The post-zygapophyses make an acute angle with 

 each other, the valley between them deeply hollowed out, and 

 in No. 25 they are deeply channelled on the upper surface. 

 Pre-zygapophyses long and expanded distally. 



Pelvis. 



The pelvis is broad, with the centre of the acetabulum in 

 the centre of the ilium. The pre-acetabular portions of the 

 ilia are deep, and produced forwards in front of the neural 

 spine of No. 28 vertebra. Dorsad they meet in a sharp ridge, 

 which is often curved in an axial direction. The ilia begin to 

 diverge at the anterior margins of the acetabula, and form a 

 broad pelvic disc, the angle of divergence being about 90°. 

 The post-acetabular portions of the ilia are produced back- 

 wards beyond No. 46 vertebra ; their lateral surfaces are 

 perpendicular and short, forming ventrad a sharp ridge 

 which does not descend so much as in Meionornis, but 

 more so than in Pachyomis . Ventral surfaces of the sacral 

 vertebras as in Meionornis. The transverse processes of the 

 posterior vertebras, 40 to 44, very oblique. The ischia pro- 

 ject considerably beyond the ilia. 



Sternum. 



The body is quadrate, or broader than long ; with strong, 

 straight lateral processes, which do not diverge much. Median 

 process long. Anterior border slightly curved ; the costal 

 processes large, slightly directed dorsad. No coracoid nor 

 pneumatic depressions. 



