830 PROF. ST. GEORGE MIVART ON .THE 
The THIRTY-SEVENTH VERTEBRA! has its neural arch provided with a pair of small 
prezygapophyses for articulation with corresponding and similar postzygapophysial 
processes extending from the neural arch of the last sacro-caudal vertebra. 
It has a small neural spine and transverse processes inclined slightly ventrad ; 
and each transverse process bears a more or less marked pit or depression on its pre- 
axial surface, indicating a distinction between its diapophysial and parapophysial ele- 
ments. ‘There is no hypapophysis. 
‘The THIRTY-EIGHTH VERTEBRA is similar to its predecessor, except that its zygapophysial 
processes are a little longer, and also its transverse processes. 
The THIRTY-NINTH VERTEBRA is like the thirty-eighth; but its transverse processes are 
slightly longer. 
The FORTIETH VERTEBRA has slight postzygapophysial processes to its neural arch as 
well as prezygapophysial ones. It has also generally a small preaxially extended 
hypapophysis at the preaxial margin of its centrum. This process may be medianly 
divided, however (as in No. 70. 3. 30. 1. in the British Museum), or may be wanting 
although there are six caudal vertebree and four sacro-caudals (as in No. 64. 2. 20. 1. 
in the British Museum). ‘The transverse process is thicker, but not quite so extended 
laterally as in the preceding vertebra. 
The FORTY-FIRST VERTEBRA.—This is like the last ; but the neural spine is not quite so 
dorsally extended; the transverse processes are shorter, more swollen, and more antero- 
posteriorly extended; the hypapophysis is much larger and bifold, being medianly 
grooved on its ventral aspect. 
The FORTY-SECOND VERTEBRA is smaller in all dimensions, except that its hypapophysis 
is still larger than in the vertebra last noticed, and is curved strongly preaxiad as well 
as ventrad. 
The PYGOSTYLE consists doubtless of many vertebree united; but it plainly consists 
(even in the adult) of the vertebra ankylosed together. The whole structure forms a 
plate antero-posteriorly and dorso-ventrally extended, but thin transversely. Its dorsal 
margin is convex, its preaxial one concave and irregular; its ventral margin is strongly 
convex for the preaxial three fourths of its extent, and strongly concave for the rest; 
it meets the dorsal margin at its postaxial end, so that the whole plate ends postaxially 
in a strongly curved pointed process, extending postaxiad and ventrad. 
The dorsal part of the plate is, of course, formed of coalesced neurapophyses, and its 
ventral part of coalesced hypapophyses. There is a more or less marked antero- 
posteriorly extended ridge on each side, formed of coalesced transverse processes. 
Often two superimposed foramina (one dorsal, the other ventral of the lateral ridge), 
mark off a small anterior part as the ultimate visible vertebra from the much larger 
* This is, of course, the thirty-sixth when there are but three sacro-caudals. 
