of Vertebra from Cape Colony. 337 



known from the Karroo rocks of South Africa. It is in a 

 poor state of ])reservation, having travelled from higher 

 ground, and by rolling has lost the neural spine, zyga- 

 pophyses, facets for the ribs, and is otherwise worn. But 

 exposure has removed much of the intractable matrix, and I 

 have cleared enough of what remained to show the more 

 important characters of the vertebra. It is an inch and a 

 half long, with the centrum laterally compressed, showing 

 intercentral facets, with a central notochoidal pit impressing 

 the centre of each articular face. The neural arch is not 

 cons|)icuously elevated, is somewhat widened in front, and is 

 deeply excavated on the under surface for pneumatic foramina, 

 in the manner seen in the cervical vertebrae of birds and 

 vertebree of Saurischian Dinosaurs. The external surface- 

 layer of bone is dense and smooth. 



Tlie anterior articular face of the centrum (fig. 1, C, p. 338) 

 is wider transversely than deep, measuring fully six tenths of 

 an inch from the neural canal to the notched-out articular facet 

 for the intercentrum, and is eight tenths of an inch wide. This 

 surface of the centrum is convex from the central pit outward, 

 resembling the faces of the vertebras preceding the caudal 

 fin of an Ichthyosaur, suggesting free movement ; but it is 

 slightly rubbed and weathered. 



The facet for the intercentral ossification (I) is triangular, 

 wider than deep, placed below and behind the vertical arti- 

 cular face, and in lateial view looks obliquely forward and 

 downward, is rounded from side to side, and has the aspect 

 of excavating the base of the articular face (fig. 2, A.I). 



Ihe posterior articular face of the centrum (tig. 1) has a 

 much smaller intercentral facet, chiefly resulting from its less 

 depth and more lunate form. The total depth of the posterior 

 surface of the vertebra a little exceeds the anterior depth 

 (tig. 2, P.C), so that the articular face of the centrum was more 

 nearly circular ; it is inclined a little forward, making the 

 measurement along the neural canal about one tenth of an inch 

 shorter than along the ventral margin. A series of such 

 vertebrae would be concave on the dorsal aspect, like the 

 vertebrge of the neck, elevated in the usual way. 



The body of the centrum measures about one inch and one 

 tenth from front to back, along the narrow concave ventral 

 surface, between the anterior and posterior margins of the 

 intercentral facets. This inferior part of the body of the 

 vertebra is somewhat flattened from side to side, with a deep 

 median longitudinal groove in its middle length (tig. 1). It is 

 compressed from side to side, with the transverse width reduced 

 to little more than a quarter of an inch, at a quarter of an 



