SYSTEMATIC REVISION Zf 



and outwards, terminating in the simple diapophysis, with rib articulation. 

 The inferior articular faces of the arch are two on each side, one for the 

 central element in front, and the other for the one behind it. The whole is 

 surmounted by a continuous neural spine, which is expanded at the summit 

 in the known species. The vertebrse do noi differ much in different parts 

 of the column. The cervicals are not distinguished in any way from the 

 dorsals, but their anterior intercentra have more extensive costal surfaces, 

 which give the inferior posterior border lateral angles. The diapophyses of 

 the second and third cervicals are of reduced size. The neural spine of the 

 axis is a little less elevated, and is longer anteroposteriorly than that of the 

 third and succeeding cervicals. I do not possess an entire atlas free from 

 matrix. Attached to the axis of this specimen are two elements which con- 

 nected it with the skull, as they are separated from it only by closely fitting 

 fractures. The elements are lateral, and each presents a semi-spherical, 

 articular face in front, and a long process with acute apex at right angles 

 to it, posteriorly. These processes lie, one on each side of the neural spine 

 of the axis, above the position which would be occupied by its prezygapophy- 

 sis ; they represent the distinct halves of the arch of the atlas. At the superior 

 base of each process near the edge of the articulation is a button-like tubercle, 

 which represents a prezygapophysis; the inferior articular faces correspond 

 with those of the occipital condyles in form but not in position, which is 

 inverted. The inferior elements of the atlas are lost. 



"The intercentra are rather longer and more elevated in the sacral region. 

 One only can be properly said to belong to the sacrum, and this is closely 

 united with the one that follows it by a rough surface of contact. In old 

 animals it may become coossified. What the relations to the intercentrum 

 immediately preceding may be, I am unable to state, owing to the condition 

 of the specimen. A pair of caudal vertebrse are peculiar. Their intercentra 

 are in contact throughout, excluding the pleurocentra. The latter rest above 

 the intercentra and between the inferior parts of adjacent neural arches. Each 

 intercentrum supports a coossified chevron bone, and these, in the two ver- 

 tebrse in question, become coossified with each other, forming a robust rod 

 directed backwards, whose double base is perforated by the hcemal canal. This 

 peculiar structure probably belongs near the extremity of the caudal series, as 

 the anterior caudals observed in other specimens are much like the dorsals. 



"The costal articulations are everywhere undivided, and have an ob- 

 liquely vertical extension. The articular surface extends to the intercentrum 

 in the E. megacephalus, forming a short superficial depression which enters 

 from the supero-posterior border. The costal surfaces of the diapophyses 

 become more robust anteriorly and are more narrowed, especially at the 

 middle and inferior portions, posteriorly. The diapophysis of the sacral 

 vertebra is very robust, and presents a large tubercular face downwards 

 and a little backwards. The external side of the intercentrum about its 

 superior angle is also covered by a large capitular facet, and the two facets 

 support a sacral rib. This element is much more robust anteriorly than the 

 true ribs, and its capitular and tubercular facets are distinct from each 

 other, although they are separated by a slight interruption. The body of 

 the rib is plate-like and is directed downwards and backwards, its union with 

 the ilium being squamosal. The costal elements posterior to the sacrum 

 diminish rapidly in size. From the size of the vertebrae in E. megacephalus, 

 the tail is probably of medium length only. 



