LIASSIC FORMATIONS. 
55 
wliicli is single and slight ; and it includes upwards of thirty vertebrae. These vertebrae, 3 
lines in length of centrum in the first five, progressively increase to a length of 1 inch at 
the twelfth, begin to shorten gradually after the fifteenth, the twenty-first being 11 lines, 
the twenty-fourth 9 lines, the twenty-eighth 6 lines, and the thirtieth 5 lines in length. In 
breadth or thickness the vertebrae decrease from the first to the tenth; and then again 
gradually from the fifteenth to the last, which is filiform. 
The first caudal, or the first of the series here preserved, has the anterior articular 
surface of the centrum subconcave. The inferior surface describes a slight concavity 
lengthwise ; the upper part of the anterior half projects as a parapophysis, the end of 
which has been broken off, showing the open cancellous structure. A ridge from its upper 
part was continued to the fore part of the anchylosed neural arch. This arch developed 
zygapopliyses, of which the anterior extend beyond the centrum ; but they are better 
shown in succeeding vertebrae. 
In the second caudal the base of the parapophysis has receded and now projects from 
the upper part of the side of the centrum, occupying more than its middle third. Part 
of a quadrate spinous process is here preserved, projecting above the centrum as far as 
the vertical diameter of that element. 
In the third caudal the base of the parapophysis, reduced in vertical thickness, 
occupies the same positions and longitudinal extent. The postzygapophysis, after a deep 
hind notch of the neurapophysis, curves over the prezygapophysis of the succeeding 
vertebra, which enters that notch. 
In the fourth caudal the base of the parapophysis has lost in longitudinal as well as 
vertical extent, and is more posterior in position. The subconvexity of the hind articu- 
lation of the centrum is here well shown. The confluent neural arch is low, attached to 
rather more than the fore half of the centrum. The postzygapophysis does not extend 
back beyond the centrum ; the prezygapophysis is continued beyond the front or concave 
surface of the centrum into the neural notch of the preeeding vertebra. 
In the fifth caudal the parapophysis is smaller and more posterior. The neurapo- 
physis rises from the anterior half of the side of the centrum and continues to show the 
zygapophysis, though reduced in size. Between the fifth and sixth caudals a small, 
slender haemapophysis {h) has been articulated to the under part of the intervertebral 
space. 
The reduced parapophysis is continued from the sixth caudal ; this vertebra shows a 
much reduced indication of neurapophysis. The base of a hsemapophysis crosses the lower 
part of the space or joint between it and the seventh caudal, then expands both forward 
and backward, and more so in the latter direction ; the inferior border of this expansion 
is straight. 
In the seventh caudal the prezygapophysis is still indicated, though much reduced in 
size. The hsemapophysis, similar in shape to the preceding one, is longer ; and three bone- 
tendons rise from the side of the hind projection of this hmmal arch. 
