.MKK'K'IA.M: TKIASSIC 1CHT1IY()SAC!;I A. 1-r, 



fessor James Pen-in Smith to be of nearly the same age as the Middle Triassir 

 horizon of the \Yest Hmnholdt Range."'" 1 



The best specimen (no. 10(>L'()) consists of ribs, caudal vertebrae, and the 

 epipodial limb elements, which were discovered in place in the limestone. Its 

 characters differ from those of typical ('. y>/.sny.sm- and j>el nun* of the type lo- 

 calities, and it appears to be necessary, for the present at least, to consider il 

 as a distinct species. The lateral apophyses of the caudal vertebrae present are 

 reduced to small rounded projections situated a short distance below the middle 

 of the sides of the centrum. The vertebrae may IDC considered as representing 

 the anterior or middle portion of the caudal region. The centra are consider- 

 ably higher than wide and their anteroposterior diameter is relatively short. 

 The anterior and posterior faces are so deeply concave that the central parti- 

 tion is almost if not quite broken through. The concave faces show a little 

 peripheral flattening, but the sharpness of the concavity in the middle portion 

 is not greatly in excess of that near the marginal area. 



An upper arch associated with a centrum is considerably flattened laterally, 

 though the summit of the blade is quite thick. The thickness is, however, 

 nearly uniform for almost the whole of the anteroposterior diameter of the 

 summit of the dorsal spine or blade. The summit is excavated or deeply 

 pitted. The zygapophyses are much like those in the anterior portion of the 

 caudal region of C. petrinus. 



MEASUREMENTS OF A CAUDAL VERTEBRA, NO. 10620. 



J loiirht of centrum 138 mm. 



Transverse diameter of centrum 104 



Anteroposterior diameter of centrum 53 



Height of an upper arch 85 



Anteroposterior diameter of an upper arch 52 



Thickness of an upper arch at summit 18 



Accompanying the vertebrae in specimen 10620 there are several ribs. They 

 are round in cross-section near both the proximal and distal ends. The shaft 

 increases in diameter very considerably at the rib head, but does not show much 

 lateral compression. The articular face appears to be hollowed out to a con- 

 siderable extent. 



Associated with the ribs and vertebrae of no. 10620 there are two bones 

 (pi. 13, figs. 4a and 4&) which do not correspond exactly in form to any ele- 

 ments that have been seen in other material thus far examined. They are 

 elongated, with a long diameter a little less than the height of the vertebral 

 centra. The middle portion is very slender, with a nearly round cross-section, 

 and a diameter equaling about one-sixth of the length. Both ends are much 



"" See list of species, p. 19. 



