SHTJFELDT : OSTEOLOGY OF THE STEGANOPODES 195 



after which it gradually disappears (never to form a completed tube), to be gone 

 entirely in the thirteenth cervical. 



In the eighth vertebra the anterior part of the carotid passage is a solid, closed 

 tube, its parapophysial walls being thick and strong, the passage of considerable 

 caliber, and the whole occupying more than the anterior third of the ventral aspect 

 of the bone. It also shows, ventrad, a mid-longitudinal ridge, with a longitudinal 

 gutter upon either side of it. This carotid canal remains a closed tube to include 

 the fourteenth vertebra, slowly changing in character as we near the dorsal series. 

 In the fifteenth to the seventeenth inclusive, its place is taken by a well-marked 

 haemal spine a character entirely absent in the eighteenth vertebra, which is a true 

 dorsal one. 



No evidence of a haemal spine whatever exists in the three fused dorsal vertebrae, 

 and in them the neural spine is but represented by a coossified, flattened ridge, 

 hardly at all higher than the fused metapophysial track at the ends of the dia- 

 pophyses, on either hand. Lateral canals begin in the third vertebra and persist to 

 the sixteenth inclusive. They are long and of small caliber in the third, fourth, 

 fifth and sixth, materially shortened in the seventh ; somewhat more so in the 

 eighth, where, for the first time, their anterior opening looks directly dorsad, which 

 latter continues to be the case in the ninth, tenth, eleventh, twelfth, thirteenth 

 and fourteenth, the canals increasing in caliber, but at the same time shortening in 

 length as we pass through the series just named. In the fifteenth and sixteenth 

 vertebrae, the lateral canals are parallel with the neural canal, about one third 

 smaller in size, their ventral floors being formed by the pleura pophysial elements. 

 For the most part the comparatively rather small neural canal is subcylindrical in 

 form, being most compressed vertically as we pass towards the distal cervicals, to 

 become more cylindrical again in the ultimate free dorsal. After passing the fourth 

 cervical, and from thence on to include the sixteenth, this tube is markedly of 

 greater caliber behind than it is in front, in any single vertebra of this part of the 

 spinal column. 



This character can be particularly well seen in the eleventh cervical. Through- 

 out, the parapophysial styles are very short. On the third vertebra they are far 

 apart, but gradually approach each other and the median line to include the sixth 

 cervical. Their character changes in the seventh, where they become sharp, short, 

 and spiculiform. In the eighth, ninth and tenth they are represented by mere 

 spinelets, close together mesiad and are to be found on the postero-ventral border 

 of the carotid canal. From this on they gradually separate again, and entirely 

 disappear from the ultimate cervical vertebrae. 



