442 . J. W. HTJLKE OlSr IGITANODON- PRESTWICHll 



neck of this Iguanodon certainly contained not less than 9 vertehrse. 

 From the foremost of these preserved, 'No. 1 (probably the third in 

 natural sequence) to the 7th, and indeed through the 8th and 9th, 

 which in general form most resemble cervical centra, a gradual 

 increase in bulk of the vertebral column takes place from the head 

 to the trunk, and a gradual ascent of the parapophysis is ob- 

 servable. 



The following measurements show the dimensions of Nos. 2 and 3, 

 the least distorted centra in this series : — 



JS^o. 2. No. 3. 

 mm. mm. 



Length along upper surface of centrum 41 • 40'5 



„ „ loAver „ „ 35-5 41* 



Diameters. 



Anterior surface, vertical 25 26 



,, „ horizontal 37 42 



Posterior surface, vertical 30 31 



„ „ horizontal 40 41 



Horizontal diameter at middle of centrum 29 36 



The typical cervical vertebrae are followed by a few in which the 

 anterior articular surface becomes plane, and the posterior is less 

 hollow. In these there is no rib -head facet upon the centrum ; but in 

 one (PL XIX. fig. 5), Wo. 11, which retains a large part of its neural 

 arch, this facet is on the anterior margin of the (upper) transverse 

 process, very close to the prsezygapophysis. It is an oval, 17 X 19 

 millims.j directed outwards, and indicates a rib of considerable 

 stoutness. The transverse process — diapophysis — is broken off just 

 beyond the rib-facet. It had a broad basal attachment to the arch 

 in the level of its crown, extending from the prse- to the postzyga- 

 pophysis, after the manner of the platform mentioned by Prof. 

 Owen as characteristic of Igiianodon Mantelli. This platform is 

 upborne by a strong buttress, which rises obliquely forwards to its 

 under surface from the lower and back part of the neurapophysis 

 near the neuro-central suture. In front of this buttress is the para- 

 pophysial facet, and behind it is a deep three-sided hollow. The 

 prsezygapophyses of this vertebra look upwards and inwards. A 

 line drawn perpendicularly to the plane of the left prgezygapophysis 

 includes, with the spinous process, an angle of about 45°. The 

 sides of this centrum (No. 11) are concave longitudinally and gently 

 convex vertically. The keel is less strongly marked than in the 

 cervical vertebrae. The length of the neural surface of this centrum 

 is 50*5 millims., and the vertical diameter of the articular ends is 

 38 millims. The length of lYo. 10 is 42 millims. 



In No. 13 the rib-head facet lies further outwards from the prae- 

 zygapophysis upon the transverse process than in No. 11. This 

 vertebra is therefore thought to have occupied a place in the ver- 

 tebral column posterior to No. 11. The length of the centrum, 

 measured along the neural surface, is 55 millims. ; and the vertical 

 diameter of the articular end is 46 millims. The sides are much 

 crushed; but it is evident, notwithstanding this mutilation, that 



