HYRACHTTJS. 663 



by its posterior border. I cannot discover the sutural boundaries of the 

 mastoid bone, but that separating the paroccipital pi'ocess from the post- 

 tympanic process in front of it is distinct. The condyle of the mandible 

 is massive, and the posterior border of the latter extends backward with 

 a slight obliquity. The foramen magnum has prominent supero-lateral 

 mai'gins which are nearly straight, and unite at a right angle above. 



Measurements. 



M. 



Elevation of sagittal crest above foramen magnum 045 



Width of bifurcation of crest bebind 033 



Width of occiput behind meatus auditorius 070 



Width between and inclusive of occipital condyles 046 



Width temporal fossa at meatus 050 



Width meatus auditorius 012 



Width condyle of mandible 032 



Depth of ramus behiud , 095 



Vertebrce. — In this specimen the vertebrse anterior to the tail are fully 

 preserved. There are seven cervicals, eighteen dorsals, seven lumbars, and 

 five sacrals. As usual the seventh has no vertebrarterial canal. The atlas 

 is deeply incised anteriorly above. It is rather short, and its traverse pro- 

 cesses are flat, thin, about as long as broad, and with regular convex distal 

 margin. The arterial foramen issues some distance above and within the 

 notch which marks the anterior base of the transverse process. It enters at 

 the notch at the posterior base. The neural arch is quite convex, and its 

 anterior margin is obtusely rounded. The axis is near the same length, 

 and bears a prominent and elongate laminate neural spine. Its diapara- 

 pophysis is narrow and overlaps the parapophysis behind it three-quarters 

 of an inch; it is pierced for the cervical artery. The centra of the third 

 and fourth cervicals are about equal in length to that of the axis, but the 

 remaining ones shorten successively to the seventh, which maintains a 

 length somewhat greater than its width. The parapophyses of these, except 

 the seventh, are flattened, and hav3 considerable anteroposterior extent, 

 their extremities overlapping. A short and rather narrow and stout diapo- 

 physis is present on the sixth cervical ; on the seventh it is larger, and espe- 

 cially expanded anteroposteriorly at the base and truncate. There is no 

 parapophysis. The fourth, fifth, sixth, and seventh have strongly opistho- 

 coelous centra; that of the third is injured. 



