288 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 



of the process, near the posterior border, a prominent, rib-like elevation 

 runs obliquely outward and backward from the side of the inferior arch to 

 the posterior angle of the process, where it ends in a rounded tubercle. 



The axis is relatively longer and narrower than in Hapalops longiceps 

 and has a prominent ventral keel ; the anterior cotyles rise higher upon the 

 sides of the neural canal, which is higher and narrower and more circu- 

 lar; the spine is a large, hatchet-shaped plate, which differs from that of 

 Hapalops in the upward slope of the much thickened posterior border ; 

 the transverse process is long and slender and the vertebrarterial canal 

 is shorter than in Hapalops. The third and fourth cervicals differ little 

 from those of the latter genus, except that the spine, which is considerably 

 higher on 3 than on 4, is higher and more pointed. 



The twelve thoracic vertebrae associated with No. 15,561 are from dif- 

 ferent parts of the region. The anterior thoracics have small centra, which 

 are somewhat contracted in the middle ; the neural spines are longer and 

 more slender than those of Hapalops longiceps and have a stronger back- 

 ward inclination, while the tips are more thickened and rugose. In the 

 hinder part of the region the vertebras have short and massive centra, 

 which in the last two have a median keel and a pair of very small ventral 

 foramina ; the neural spines are shorter and much narrower than in H. 

 longiceps, but with much heavier tip; the spine of the last thoracic is 

 much broader than that of the penultimate one ; transverse processes 

 are prominent on all and even the last one appears to have a facet for the 

 tubercle of the rib ; metapophyses are first distinguishable on the antepe- 

 nultimate vertebra, suddenly becoming very prominent on the penultimate. 

 Accessory zygapophyses are present only on the last vertebrae, or, per- 

 haps, on the last two. 



Four lumbar vertebrae are present ; they have centra of nearly uniform 

 length, becoming broader and more depressed posteriorly ; all have the 

 ventral keel and foramina, but the latter are conspicuous only on the third 

 and fourth, and largest on the third ; the neural spines are lower, broader 

 and more erect than those of the posterior thoracic region and are shorter 

 than the lumbar spines of Hapalops longiceps ; the transverse processes 

 are shorter and less antroverted than in the latter species, and the acces- 

 sory zygapophyses are like those common to all the family. 



The sacrum consists of five vertebrae, of which the first is less com- 

 pletely incorporated than the others and seems to belong to the lumbar 



