15 



side of the neural spine of the axis, above the position which would be occu- 

 pied by its prezygapophysis ; 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 intercen- 

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

 condition of the specimen. A pair of caudal vertebrae 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 iutercentrum supports a coossified chevron 

 bone, and these, in the two vertebra; in question, become coossified with 

 each other, forming a robust rod directed backwards, whose double base is 

 perforated by the hsemal 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 oblique- 

 ly 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 supe- 

 rior angle is also covered by a large capitular facet, and the two facets sup- 

 port 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 but 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 posterier to the 

 sacrum diminish rapidly in size. From the size of the vertebrae in E. meg- 

 aceplialus, the tail is probably of medium length only. 



The coracoid is but little incurved ; its internal border is convex, and is 

 roughened as though for cartilaginous attachment. Its superior portion forms 

 a convex continuum with the scapula. The direct line or external face of 

 "the scapula extends in a nearly plane surface to the glenoid cavity, em- 

 bracing a perforating foramen above the latter, precisely as in the Pelyco- 

 sauria. Its surface is continuous anteriorly with a wide expansion forwards, 

 whose fine inner border is continuous with that of the coracoid. This 

 plate doubtless includes a third element, but its borders are not preserved, 

 on account of the obliteration of the sutures. It is probably epicoracoid, 

 as in the Pelycosauria. In its form it is less produced than in the known 

 scapular arches of the latter. 



