EDENTATA OF THE SANTA CRUZ BEDS. 47 



moderate ventral keel and lateral ridges that converge forward. The co- 

 tyles for the atlas extend farther below the centrum than in Stegotheritim. 

 The pedicles of the neural arch are rather narrow and are each perforated 

 by a foramen ; the spine is not much elongated antero-posteriorly, but is 

 very high, much higher than in Dasypus, and belongs almost entirely to 

 the axis. The transverse process is considerably longer than in Stegothe- 

 I'/Hin, but is comparatively slender for most of its length, thickened and 

 club-shaped at the free end ; the anterior opening of the arterial canal is 

 lateral, not ventral. 



The fifth cervical has a short, broad, depressed centrum, which on each 

 side extends out beyond the centrum of the fourth vertebra, clasping it be- 

 hind, as it were ; posteriorly, it is itself clasped in the same fashion by the 

 sixth, giving the ventral side of these vertebrae a very peculiar appearance. 

 Something of the same kind may be observed in Dasypus and, more dis- 

 tinctly, in Priodojites. The centrum of the fifth cervical is somewhat con- 

 cave from side to side and the transverse process is a long, depressed plate, 

 which extends almost directly out from the centrum with very little back- 

 ward inclination ; the neural arch is extremely slender and the neural spine 

 distinct. 



The sixth cervical resembles the fifth, but has a shorter, wider centrum, 

 somewhat heavier transverse process and a thread-like neural arch, without 

 spine. 



The seventh cervical considerably exceeds the sixth in every dimension. 

 On each side of the centrum is a rugosity, which bears a facet for the 

 head of the first rib, and the transverse process is long and heavy and 

 somewhat thickened at the distal end. The neural arch is not quite so 

 slender as that of the sixth and there appears to be no spine. 



The first thoracic vertebra has a short, broad centrum, which, however, 

 is narrower and longer than that of the last cervical, and is decidedly 

 opisthoccelous ; the transverse process is very large, projecting far out 

 from the side of the centrum and much produced vertically ; it bears a 

 large, saddle-shaped facet for the connate head and tubercle of the pecu- 

 liar first rib. This vertebra has the longest neural spine of any in the 

 entire column ; this spine is thin and compressed, becoming very slender 

 near the end, though the tip is slightly thickened, and is almost vertical. 

 The second thoracic is steeply inclined upward from the first and has a 

 considerably longer and narrower centrum, which contracts posteriorly. 



