320 PROFESSOR OWEN ON IHE SKELETON 



hinder and lower portions afterwards alone represent this process ; the neural spine is 

 a higher tubercle than in the twelfth vertebra. 



The fourteenth vertebra, retaining its pleurapophyses as free elements, may be 

 reckoned as the first dorsal (PI. LI. fig. 1, d) ; its centrum is broader than it is long, 

 with a medial and two marginal ridges below : the first ridge is hypapophysial ; the 

 latter are parapophysial, and are most produced, each bounding a concavity on the 

 under surface of the vertebra. The pleurapophysis (ib. pi) is a simple, straight style, 

 6 lines in length, articulated to the under part of the base of the diapophysis, which is 

 now a broad, triangular, depressed plate. The neural spine is a strong, compressed, 

 quadrate plate in this and the succeeding dorsals. 



In the second dorsal the parapophysial or lateral hypapophysial ridges are more pro- 

 duced, especially at the hinder angle. The pleurapophysis is a long, nearly straight 

 style of about 3 inches in length, and supports at the beginning of its lower or distal 

 third an epipleural plate curving upward. The head of the rib is expanded and articu- 

 lates to much of the under part of the diapophysis. The quadrate neural spine gains in 

 fore-and-aft extent. 



In the third dorsal the lateral hypapophysial plates are longer and narrower, and 

 begin to be supported as processes from the descending inferior part of the centrum. 

 The pleurapophysis, 3 inches 7 lines in length, articulates above by a head and tubercle 

 wuth the centrum and under part of the diapophysis, and below with a straight hsemapo- 

 physis, 1 inch 5 lines in length, and expanding at its sternal end to articulate with an 

 oblong cavity, transverse to the broad costal margin of that bone. The epipleural is a 

 plate 1 inch in length, and from 1 to 2 hues broad. 



In the fourth dorsal (PI. LII. fig. 7), the parapophyses are converted into a hypapo- 

 physis in the form of a broad bifurcate process, the prongs diverging at a wide angle as 

 they descend from the common produced base {hy). The pleurapophysis, with the 

 head more distinct from the tubercle, and supported on a longer neck, is 4 inches in 

 length, and articulates with a hzemapophysis 1 inch 10 lines in length. The diapo- 

 physes (ib. d) are long and broad ; the zygapophyses (ib. z, z) small and short. The 

 neural spine (ib. ns) increases in antero-posterior but not in vertical diameter, and 

 preserves the quadrate form. 



In the fifth dorsal, the stem of the bifurcate hypapophysis lengthens. The pleurapo- 

 physis, 4 inches 10 lines in length, continues as slender as the preceding, and articu- 

 lates with a hsemapophysis 3 inches 2 lines in length, and slightly bent. 



The sixth dorsal has a longer and narrower stem of its bifurcate hypapophysis ; but 

 the fork is broken off. The pleurapophysis is as in the fifth, but with a longer and more 

 curved hsemapophysis, 4 inches in length, and with a rather shorter epipleural lamina. 

 In the seventh dorsal the hypapophysis is a compressed subquadrate plate, a little 

 expanded at its lower margin. The pleurapophysis, 6 inches in length, retains its 

 slenderness ; the hsemapophysis is 4 inches 8 lines in length. 



