Structure and Affinities of the Endothiodont Reptiles. 267 



the level of the upper border of the body there is developed what 

 is evidently a robust transverse process. There is no trace of a rib, 

 but it seems probable that a small rib has been articulated to the 

 lower side of the transverse process and the outer side of the body. 

 The posterior zygapophyses lie for the most part inside of the pre- 

 zygapophyses of the third cervical vertebra. The axis has a fairly 

 prominent spine, but it is not much developed antero-posteriorly. 



Beyond the axis there are preserved three cervical vertebrae which 

 may be the third to the fifth, but it is perhaps more probable that 

 they are the fourth to sixth. The three vertebrae very closely 

 resemble each other, and they also resemble pretty closely the 

 axis apart from the odontoid process. For convenience they will 

 be referred to as the fourth, fifth, and sixth. The body of each 

 vertebra has similar lateral grooves to those seen in the axis. The 

 front half of the under side of the body is moderately flat trans- 

 versely and forms on each side a small tubercle for the rib. The 

 transverse processes are very well developed and pass directly 

 outwards on a level with the upper border of the body. The total 

 width of each vertebra is a little less than three times the width of 

 the body. The spines are lost and the structure of the zygapophyses 

 is not well shown. The structure of the proximal ends of the ribs 

 of the three vertebrae is fairly well seen. Each rib is double-headed 

 and the two heads are rather widely apart, the one articulating with 

 the lower outer and anterior corner of the centrum, and the other 

 with the under side of the outer part of the transverse process. The 

 portion of the rib between the two articulations makes with the shaft 

 an appearance like the letter Y. The shaft is slender. 



The next series of vertebrae are probably the seventh to the 

 eighteenth. The first of the series resembles pretty closely the sixth 

 cervical and is probably the seventh cervical. The rest of the 

 vertebrae are probably all dorsals. The seventh cervical is slightly 

 imperfect. It differs from the more anterior cervicals in having the 

 ribs more robust. The shaft of the rib passes backwards, outwards, 

 and downwards ; and though the rib is still two-headed, the surface 

 for articulation with the underside of the transverse process is so 

 long that it almost joins the articulation for the centrum. 



The vertebra which follows the s apposed seventh cervical and 

 which is probably the first dorsal shows the centrum to be slightly 

 different from that of the more anterior vertebrae. The articulation 

 for the head of the rib forms a less marked tubercle owing 

 apparently to the head of the rib articulating in part with the 

 interarticular fibro-cartilage. In the second dorsal the tubercle is 

 less developed than in the first, while in the third dorsal the 



