246 PROCEEDINGS OF THE NATIONAL MUSEUM VOL, 92 
As in that genus, it strongly overhangs the anterior half of the cen- 
trum and presents a thickened anterior border that is slightly hollowed 
out longitudinally. 
Cervical vertebrae posterior to the axis ——Six vertebrae are consid- 
ered as constituting the complete cervical series. The type speci- 
men has the second, third, fourth, and fifth cervicals preserved, where- 
as all are present in U.S.N.M. No. 15816. The principal modification 
to be observed between the third and sixth vertebrae, inclusive, is an 
increase in size of the diapophyses and a progressively more erect 
posture of the neural spines. The neural spines are relatively narrow 
anteroposteriorly, with a thickened posterior border and a sharp an- 
terior edge. The top is thickened transversely, with a diagonally 
truncated end that in the posterior members of the cervical region is 
broadly notched. The sixth spine is perceptibly widened fore and 
aft. A small diapophysial process on the third cervical may have 
borne a small cervical rib, as indicated by the smooth articular sur- 
face of its end. This process on the fourth cervical is more robust, 
being elongated dorsoventrally and constricted near the middle, thus 
dividing the articular surface into two costal facets. These facets 
have a decided diagonal trend, the lower border projecting downward 
shghtly below the level of the centrum on the fifth and presumably 
on the sixth cervical. The diapophyses reach their maximum size on 
the sixth. The centra are relatively short, subequal in size, evenly 
rounded on the ventral surface, and have a subcircular ball and cup. 
A heavy rounded ridge runs diagonally downward and backward 
from the top of the diapophyses to the edge of the ball. Below this 
ridge the side of the centrum is slightly excavated. The ridge joining 
the prezygapophyses and postzygapophyses is broadly hollowed out 
at the center. All these vertebrae have a well-developed zygantral- 
zygantrum articulation. 
Intercentra are present in articulated position in specimen U.S.N.M. 
No. 15566, at the junction of the second and third and of the third 
and fourth cervicals, as clearly shown in plate 25. There are no 
distinct articulating facets for these elements, asin 7guana and Cyclura, 
their broadened bases resting smoothly across the junction of the 
centra. As mentioned previously, the downward-projecting process 
on the anterior ventral border of the axis may be a coalesced 
intercentrum. 
As articulated, the five anterior vertebrae in specimen U.S.N.M. 
No. 15566 have a total length of about 64 mm. 
Measurements of cervical vertebrae of the type (U.S.N.M. 15477) (in millimeters) 
2 3 4 5 
Greatest length of 7centrum= 22 = es eee 10.5 10 10 10. 75 
Greatest transverse width across diapophyses_____ 13 1350-4 13°67) 715.5 
Greatest; height overaliset at es ae 16 ZO AAO sh 2D 
