274 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. 



anterior pair separated from the posterior by transverse grooves. The 

 neural arch is high on Cd. i and continually decreasing in size, 

 becomes an open groove on ?i3; the spine is not distinguishable 

 beyond 6 ; the zygapophyses, which are at first very conspicuous, diminish 

 Part passu with the reduction of the neural arch, from ? 14 they are 

 mere vestigial tubercles and they are absent on ?i8. The transverse 

 processes are very long, broad and depressed on i, and, though rapidly 

 reduced in length, they are still distinct on ?i8; on 2 and 3 these proc- 

 esses have curious expansions of the distal end, are quite slender from 4 to 

 7, and from 8 to ?I3 again have well defined distal expansions. The 

 chevrons are known only from the hinder part of the tail and three are 

 present with the caudals of No. 15,314 ; these are very small canoe-shaped 

 bones, with a deep vascular channel, which is almost closed dorsally by 

 the lateral expansion of the facets for the vertebral centra; two of the 

 chevrons have each two pairs of such facets, while the smallest of the 

 three, which was apparently attached to the ? fourteenth caudal, has but 

 a single pair. 



In the subjoined table the dimensions of caudals ?u, ? 13, ?i6 and 

 ?i8 are from No. 15,314, all the other measurements from No. 9,241. 



MEASUREMENTS. 



Atlas, length 0315 Second thoracic, length of centrum. . . .018 



" width 062 " " width of anterior face .017 



" height 032 " " height 06 1 



Axis, length of centrum (excluding First caudal, length of centrum 022 



odontoid) 023 " " width of anterior face . . . .027 



" width of anterior face 0305 " " over transverse pro- 



" " posterior face 017 cesses 109 



" " neural spine (fore and " " height 037 



aft) 036 Fifth caudal, length of centrum 022 



Third cervical, length of centrum 018 " width of anterior face ... .0215 



width of anterior face .. .015 " " " over transverse pro- 

 Fifth cervical, length of centrum 018 cesses 063 



" width of anterior face . . .014 " " height 033 



Seventh cervical, length 017 Seventh caudal, length of centrum . . . .021 



" width of anterior face .015 " " width of anterior face . .020 



Neck, length in a straight line 144 " " over transverse 



First thoracic, length of centrum 019 processes 0565 



width of anterior face . . .014 " height . .030 



height (including neu- Ninth caudal, length of centrum 020 



ral spine) 059 " " width of anterior face. . . .019 



