246 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



Type. No. 9,293. No. 9,250. 



Occiput, height -036 .040 



" width at base .050 .05 1 



Distance, occipital condyle to glenoid cavity 021 .022 .023 



" &. 062 .065 .060 



Skull, width at postorbital constriction .027 .028 



" " over lachrymals .046 .047 



Zygomatic arch, length .068 .071 .066 



Palate, length in median line 044 .043 .045 



" width at 1 017 .018 .016 



preorbital fossae 021 .020 .020 



" " S. oio .0125 .010 



" " "6. OIO .OI3 .Oil 



The skeleton, which is known only from the American Museum speci- 

 men, No. 9,250, closely resembles that of H. elongatus, except in its 

 distinctly smaller size. The vertebrae are somewhat smaller than in the 

 latter, but have relatively more robust neural spines, especially in the 

 lumbar and posterior part of the thoracic regions. In the hinder part of 

 the thoracic region the foramina opening on the ventral side of the centra 

 are reduced to very small proportions, in fact, almost obliterated, while 

 in the lumbar region they remain open, reaching their maximum size in 

 the third vertebra of this series. As in H. elongatits, the sacrum consists 

 of five vertebrae, the neural spines of which are coalesced into a continu- 

 ous ridge with thickened dorsal border. The caudal vertebrae are rela- 

 tively somewhat heavier than in the last named species and have slightly 

 longer and heavier transverse processes. 



The comparatively unimportant differences between the vertebrae of the 

 present species and those of H. elongatus may be largely due to differences 



of age. 



MEASUREMENTS. 



First thoracic, length of centrum 018 Third thoracic, height of neural spine .030 



" " width of anterior face .. .014 " " width of neural spine 



" " " " posterior face . .015 at base 012 



" " " " over transverse " " width of neural spine 



processes .... ? .033 at tip oio 



" height of neural spine. ?.O3i Last thoracic, length of centrum 022 



" width of neural spine at width of anterior face . . .024 



base on " " " over transverse 



Third thoracic, length of centrum ... .016 processes 047 



" " width of. anterior face . .012 " " height of neural spine . .038 



" " " posterior face .034 " " width of spine at base . .017 



