15 
side of the nenral 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 codssified. 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 intercentrum supports a codssified chevron 
bone, and these, in the two vertelree in question, become cvdéssified with 
each other, forming a robust rod directed backwards, whose double base is 
perforated by the hemal 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 #. 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 fuce 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- 
porta 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 ilinm being squamosal. The costal elements posterier to the 
sicrum diminish rapidly in size. From the size of the vertebre in 4. meg- 
acephalws, the tail is probably of medium length only. 
The coracoid is but little incurved ; its internal border is convex, and is 
roughened asthough forcartilaginousattachment. 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, 
ag in the Pelycosauria. In its form it is less produced than in the known 
scapular arches of the latter. 
