690 



PROF. H. GT. SEELEY ON THE REPTILE 



series as probably not later than the 6th dorsal, while it might have 

 been as early as the second, which is likely to have been its true 

 position. Then succeeds a centrum which may have belonged to 

 about the fifth dorsal. The remaining six vertebrae appear to be in 

 sequence, and belong to the hinder part of the vertebral column ; 

 and if the number of vertebras was the same in this animal -as in the 

 Alligator, they might be the 7th to 12th dorsal vertebras. The 

 13th, or last dorsal or lumbar vertebra, if found separately, might 

 have been referred to another genus, and perhaps to a Dinosaur. 

 The first sacral vertebra is imperfectly preserved. 



The early dorsal vertebra is distinguished, as in existing Croco- 

 diles, by the slight development of the ridge, which ascends from the 

 hinder border of the praszygapophysis inward and backward towards 

 the neural spine. The centrum has a length of from 18 to 19 millira. ; 

 so that there is but little increase of length as compared with the 

 cervical region. The transverse process is compressed and directed 

 outward horizontally or a trifle upward. It is thickened on the in- 

 ferior posterior border by a ridge which extends downward towards 

 the centrum and constitutes a marked specific character, especially 

 as there is a deep conical pit behind it immediately below the notch 

 which separates the transverse process from the postzygapophysis. 

 The antero-posterior width of the transverse process is 11 millim. 

 Resting upon it in front, rather more horizontally than in existing 

 Crocodiles, so far as regards its lateral direction, is the praszygapo- 

 physial facet (fig. 8), which is about 11 millim. long and 6 millim. wide. 

 The transverse process is perhaps a little lower in position than the 

 transverse process in the early dorsal vertebras of the Alligator, being 

 on a level with the upper part of the neural canal. The ridges on 

 the posterior zygapophyses are rather narrow, so as to give a some- 

 what pinched aspect to the concave area on each side at the base of 

 the neural spine (fig. 8). The neural spine extended backward a 

 little between the diverging ridges of the posterior zygapophyses ; and 

 at its base there is a pit. The centrum is evenly rounded (fig. 9), 

 and both cup and ball well developed. As in the cervical region, 

 the ball is marked on its upper margin by an incised groove (fig. 8) 

 similar to that seen in the vertebras of the Alligator. 



The later dorsal vertebras, as in existing Crocodiles, are charac- 

 terized by the deeper depression between the anterior and posterior 

 zygapophyses, and by the increased elevation of the zygapophyses 

 above the transverse process, consequent upon this process acquiring 

 a somewhat lower position relatively to the neural canal. The pras- 

 zygapophyses come to extend a little further forward and to look a 

 little more upward and inward. The centrums increase in length 

 so that what I regard as the tenth is 23 millim. long. The articular 

 cup in front, perhaps, becomes a little wider : and the base of the 

 centrum is rather more flattened. The compressed appearance at 

 the base of the transverse process gives place to a regular concavity 

 from above downward ; and the antero-posterior extent of the neural 

 arch is increased, while the size of the neural canal is diminished 

 and its height lessened. There also comes to be a less development 



