426 MR. J. W. HULKE ON THE SKELETAL [NoV. 20, 



supposition, since instances of such plan of structure are common. 

 Thus in Fish the spinous processes are built up by the appositio.i of 

 a pair of flat styles primitively distinct, and this composite process is 

 segmentally separate from the summit of the neural arch to which 

 it is attached by the medium of soft tissue. 



The Crocodilian atlas is not to be regarded as a degraded vertebra, 

 but as one retaining the plan of construction common in the earliest 

 reptiles and their progenitors. Actinodon needs but the addition of 

 an internal ossification enclosing the axial part of the notochord to 

 furnish a close parallel. 



Remaiinng Cervical Fertehrce (Plate XVIII. fig. 2). — All behind 

 the two foremost possess an upper and a lower transverse process, 

 the former borne upon the arch, the latter upon the centrum. The 

 former (diapophysis) is always longer than the lower, and projected 

 outwards and downwards. Its root is in or slightly above the level 

 of the neuro-central suture, and it is nearly equidistant from both 

 ends of the centrum. The parapophyses, shorter and stouter, 

 approach closely the anterior terminal surface of the centrum. In 

 vertebrte closelj' following the epistropheus, the parapophyses occur 

 at the junction of the lateral with the inferior surface of the centrum, 

 thus augmenting the breadth of this. Between the parapophyses, 

 anteriorly, the ventral surface is depressed, whilst posteriorly, in the 

 same direction (transversely), the surface presents a low keel. Both 

 terminal surfaces of the centrum have a roughly circular outline ; 

 the anterior is nearly plane, and the posterior is distinctly concave. 

 As the trunk is approached the parapophysis ascends on the side of 

 the centrum, and the diapophysis rises on the neural arch. The 

 antero-posterior extent of the sutural attachnietit of the neurapo- 

 physis to the centrum nearly equals that of the latter. The spinous 

 process is compressed, its outline square. The zygapophyses spread 

 considerably, and the articular surfaces of the anterior have an 

 upward slant. 



Trunlc Fertebrce (Plate XVIII. fig. 3).— In the front of the 

 thoracic region of the vertebral column the parapophysis leaves the 

 centrum, and the capitular costal facet appears on the anterior 

 border of the upper transverse process, just external to the prsezy- 

 gapophysis, as in now living Crocodiles. The transverse process is 

 long, it is directed nearly horizontally outwards, and it bears at its 

 free extremity the costal tubercular joint. The figure of the centrum 

 is cylindroid, its middle is constricted. Towards the loins the para- 

 pophysial or, as it may be preferably named, the capitular costal 

 articulation moves outwards towards the free end of the transverse 

 process, where it finally coalesces with the tubercular facet, both 

 forming there one single costal articulation. 



Sacrum (Plate XVIII. fig. 4). — 'J'here are two sacral vertebrae. 

 These may be distinguished from all others by their greater massive- 

 ness, also by the stoutness and length of their transverse processes. 

 These latter are composed (1) chiefly of an inferior element which 

 ossifies independently of the centrum (with which it is united by a 

 suture that long continues distinct), and in virtue of this claims to 



