Apr. 1903. North American Pi.k.sios.urs — Wiiusion. '63 



length between that of the eleventh and of the thirteenth. On the 

 last cervical centrum, the thirteenth, the twelfth rib is long, heavy 

 and stout, more than half the length of the first dorsal. It is nearly 

 as stout as any of the following, but tapers somewhat distally, though 

 ending in a truncated, cartilaginous extremity. The distal end of the 

 eleventh rib is lost. The first dorsal rib resembles the one preceding 

 it, though longer. The second dorsal rib has acquired nearly the full 

 Length of the thoracic series. In the ninth rib there is a beginning ot 

 a diminution in size; the rib is less thick, a little shorter, and less 

 expanded at its extremity. The twelfth rib is completely preserved; 

 it is yet smaller and thinner than the eleventh, though still possessing 

 a cartilaginous extremity. Of the following ribs, only the heads of 

 some are preserved. 



Diapophyses. — The diapophyses occupy an unusually low position 

 on the arch of the whole dorsal series, as do also the cervical ribs. 

 They have not been wholly freed from the matrix, and their relation 

 to the articular process is determinable only in slight part in a few of 

 the posterior vertebrae. The arch, like the cervical ribs, is united by 

 a strong, persistent suture, evidently an adult character, since the 

 sutures of the atlanto-axial complex have been entirely obliterated. 

 The process of the first dorsal is short, compressed, and somewhat 

 expanded at each extremity, it clearly springs from below the dorsal 

 surface of the centrum. As already described, the last cervical rib, 

 but little shorter than the first dorsal rib, is attached to a short 

 process which arises, apparently wholly, from the centrum. The 

 diapophysis of the first dorsal is less than twice the length of this 

 process, and so much like it that its sutural connection with the 

 centrum is the chief distinctive difference. The second dorsal dia- 

 pophysis is a little stouter than, and about twice as long as the first. 

 Its articular surface for the rib is larger, flattened, and looks down- 

 ward and outward. The fourth and fifth processes have attained the 

 maximum size of the series. They have a narrow, concave ventral 

 border, more strongly concave posterior border, a flattened, expanded 

 proximal end for union with the centrum and an expanded distal 

 extremity with its flattened oblique costal surface. Thu height of the 

 process distally, and its expansion beyond the plane of the articular 

 zygapophyses, can not be determined. It is very evident, however, 

 that the diapophyses lie below the plane of the zygapophyses. in 

 which they differ markedly from the diapophyses of Dolichorhyn- 

 ckops, where, throughout most of the dorsal vertebrae, tin van placed 

 wholly above the plane of the zygapophyses. The succeeding dia- 



