348 R. S. Lull — Pleistocene Ground Sloth, 



intervertebral foramen. The neural canal is pentagonal in 

 shape, with a rounded angle at the summit of the arch. Its 

 height is a little less than its greatest width. The zygapo- 

 physes are well marked, the anterior ones presenting a trans- 

 versely concave face, whiJe in the postzygapophyses the reverse 

 is true. 



The vertebrarterial canal is large, bounded above by a robust 

 transverse process, while below the bone forming the floor of 

 the canal is thin, though wide in antero-posterior extent. The 

 inferior lamella of the transverse process is broken away. The 

 transverse process is deflected downward and backward. 



Dimensions. 



Centrum, ant. -post, diameter 35 mm 



depth 43-5 



width 66 



Neural canal, height 40 



width 44 



Neural arch, ant.-post. diameter over zygapophyses .. 49 



width over prezygapophyses 109 



pedicel, transverse diameter 22 



ant.-post. diameter 21 



Width over transverse processes 156 



Seventh cervical. — This is a bone in fine preservation, except 

 that it lacks the left moiety of the neural arch and the trans- 

 verse process. It articulates approximately with the sixth cer- 

 vical just described and resembles the latter in the general 

 proportions of the centrum. In this regard the bone differs 

 markedly from the dorsals. The centrum presents a somewhat 

 pentagonal anterior aspect, while on the posterior one the pres- 

 ence of the facets for the first dorsal ribs serves to flat- 

 ten the ventral margin. Yentrally the centrum bears a slight 

 keel flanked by four nutritive foramina. The rib facet on the 

 right side is well preserved and is a slightly oval, saucer-like 

 depression backed by a conical mass of bone which arises 

 from the body of the centrum. The neural arch is robust and 

 springs from, the anterior half of the centrum. It bears a 

 strong transverse process which is directed obliquely outward, 

 being deflected downward about 30° from the horizontal. 

 Distally it terminates in a slight vertical expansion. The zyga- 

 pophyses are similar to those of the sixth cervical, but are 

 of somewhat greater extent and sharper curvature along their 

 transverse axis. 



The pedicel of the neural arch is strong, but dorsally the 

 roof of the canal becomes thin and somewhat broadly expanded 

 in the antero-posterior direction. 



