82 PKOr. H. G. SEELEY ON 



neural canal (fig. 1, n, sx). The lateral margins of this triangular 

 area are approximately parallel to the external surfaces of the neural 

 arch ; only much of the external bone is broken away with the 

 cervical rib which it supported. The interval was occupied by 

 lateral air-cavities, one on each side, which included some delicate 

 supporting bony films. The four supraneural chambers thus indi- 

 cated appear to extend longitudinally throughout the neural arch. 



The superior external surface of the neural arch is very imperfect. 

 In the median line it forms a longitudinal blunt ridge from which 

 the smooth flat lateral halves of the neural arch diverge outward at 

 a wide angle (fig. 4), becoming convex as they descend, and ter- 

 minating outward in a blunt ridge, which ascends from the hinder 

 border of the diapophysial attachment of the rib, and defines the 

 upper border of a large lateral concavity on the side of the arch, like 

 an impression of the finger (fig. 2). Its lower half rests against the 

 upper half of the neural arch, and its upper part, which has a thin 

 wall, is bounded by the lateral air-chamber of the neural arch. 

 There is a small foramen in the upper anterior part of the concavity. 

 This concavity is bordered below by a strong longitudinal ridge, 

 which is placed below the middle of the side of the neural canal 

 (fig. 4). As this ridge extends forward it expands to form the 

 anterior border of the concavity, which is 2-5 centim. behind the 

 articular face of the centrum. It is prolonged further forward, de- 

 creasing in height (fig. 2). Its inferior surface is horizontal and 

 sinuous ; as preserved, it is 2 centim. long. The greatest transverse 

 measurement on it, through the centrum, is 2-5 centim. It is 

 apparently upon the line of junction of the neural arch with the 

 centrum, 1| centim. from the base of the centrum, and 2^ centim. 

 from the median ridge of the neural arch. The remainder of the 

 neural arch is badly preserved, and does not admit of description. 



The region below the neuro-central ridge is the side of the cen- 

 trum. Anteriorly it rises into the bases of the pedicels of the 

 neural arch, which curve obliquely outward and upward towards- 

 the rib (fig. 2). So much of the side of the centrum as is pre- 

 served is approximately vertical, concave from the neuro-central 

 ridge to the angle at the base of the centrum, and more gently 

 concave from front to back. At more than 1| centim. behind the 

 articular face, and half a centim. from the base, is a transversely 

 oblique foramen, over half a centim. long, margined superiorly by 

 a slight arched border (fig. 2, ^n), which extends beyond it. This 

 was probably covered by the cervical rib, and appears to have been 

 pneumatic. The least transverse measurement in the middle of the 

 centrum is 8 miUim. at the posterior fracture (fig. 4). There is a 

 slight constriction anteriorly at the base of the neuro-central angle, 

 so that the centrum bulges a little below it. 



The base of the centrum is elongated, flattened, with concave 

 sides. It is concave transversely, and widened anteriorly (fig. 3) by 

 the development of the parapophysial tubercles for the rib, which 

 extend the base till it is as wide as the centrum. At the posterior 

 fracture the transverse measurement is one centimetre, so that it 



