330 PROF. ST. GEOKGE MIVART ON. THE 



The THIRTY-SEVENTH VERTEBRA ' has its neuTal arch provided with a paii- of small 

 praezygapophyses 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 prsezygapophysial 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 A'ertebrae 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 vertebrae 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 cui-ved 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-sixtli when there are hut three saero-eaudals. 



