72 



University of California. 



[Vol. 3 



The articular surfaces of the diapophyses are confluent with 

 those for the reception of the upper arches from the anterior end of 

 the column at least as far back as the thirty-fifth or thirty- seventh 

 vertebra in osmonti (PI. 8). In the specimen of perrini 

 these two surfaces are confluent as far back as the twenty- seventh 

 vertebra, where they are suddenly separated and the diapophysis 

 moves to a lower position on the side of the centrum (PI. 7, fig. 2) . 

 It is certain that some of the anterior vertebrae belonging to this 

 specimen are absent. If they were all present, the point in the 

 vertebral column at which the lowering of the diapophyses takes 

 place would be close to the thirty-fifth vertebra, as in osmonti. 

 In the posterior dorsal region the diapophyses are low down on 

 the centra and remain in that position on the anterior eaudals, 

 but rise again slightly on the middle portion of the tail. 



Compared with the height and length of the centrum, the 

 diapophyses of the dorsals are longer and narrower than those 

 of the cervicals. In osmonti the centrum of the first vertebra 

 has a height of 39 mm., the diapophysis a height of 20 mm. In 

 the thirty-fifth, the corresponding dimensions are 73 and 50. 



On those vertebra? from which the parapophysis is disap- 

 pearing, a slight constriction may be seen about the middle of 

 the diapophysial ridge, and from this point the lower extremity 

 swings forward to the anterior margin of the centrum. Tins 

 character becomes more strongly marked toward the middle of 

 the dorsal series (PI. 8, fig. 5). 



Corresponding to the form of the vertebrae, the cervical ribs 

 (PI. 12) possess a large tuberculum and a small capitulum, the lat- 

 ter disappearing with the parapophyses. The two surfaces of ar- 

 ticulation are separated by a notch corresponding to the depression 

 between the di- and parapophyses of the centrum. Numerous 

 ribs associated with the anterior dorsals of perrini and osmonti 

 show no trace of the capitulum (PI. 7, fig. -1 and PI. 9, 

 fig. 6). In the middle and anterior dorsals, the rib head 

 exhibits variation in form corresponding in a manner to that 

 already described as occurring in the diapophyses. Though 

 the heads are of approximately the size and form of the dia- 

 pophysial surfaces, they cannot be closely fitted to them, as the 

 middle of each face is more prominent than the superior and 



