MIOCENE PORPOISES KELLOGG 141 



mm.). Dorsally the centrum is deeply depressed, and medially a 

 small foramen is located on each side of the thin longitudinal ridge. 

 An elongated facet for the capitulum of the following rib is located 

 on the upper posteroexternal angle of the centrum. 



The diapophyses are rather large and the subpyriform facet for the 

 tuberculum of the corresponding rib slopes obliquely downward and 

 inward. The prezypagophysial facets are ovoidal in outline, elongated 

 anteroposteriorly (17 mm.), closely approximated to one another, 

 and slope very slightly from outer to inner margins. The post- 

 zygapophysial facets are narrow (maximum width 9 mm.), elongated 

 anteroposteriorly (20 mm.), and slope slightly toward inner margins. 



The neural spine is broken off above the base and the backwardly 

 projecting dorsal portion of the neural arch is relatively wide pos- 

 teriorly (28 mm.). The anterior edge of each pedicle of the neural 

 arch is nearly vertical, while the posterior edge slopes upward and 

 forward. The neural canal is narrow and high. 



The eighth dorsal (pi. 15, fig. 5) has incomplete metapophyses, the 

 neural spine is imperfectly preserved, and the postzygapophysial 

 facets are broken off. 



The interval between the inner margins of the prezygapophysial 

 facets appears to have exceeded that of the fourth dorsal, the neural 

 canal is also wider (22.5 mm.), the backwardly projecting dorsal 

 portion of the neural arch is very narrow, and the width of the posterior 

 face (pi. 15, fig. 8) of the centrum is approximately the same as the 

 anterior face. 



The centrum is slightly longer (45 mm.) than broad (41.5 mm.), its 

 ventral keel is rounded, and its lateral surface curves concavely from 

 end to end. The deeply depressed dorsal surface of the centrum is 

 divided longitudinally by a thin ridge. 



The diapophyses (or coalesced diapophysis and merapophysis of 

 Abel, 1931) have a deep ovoidal depression on the anterior surface 

 and a similar slightly shallower depression on the posterior surface. 

 The subpyriform lateral facet for the head of the corresponding rib is 

 concave and projects below the dorsal surface of the centrum. 



The neural canal is somewhat ovoidal in outline (pi. 15, fig. 2). 

 Although the anterior and posterior edges of the neural spine are 

 eroded, it would appear that it was directed nearly verticallj^ and 

 that it did not slant backwards, 



CAUDAL VERTEBRA 



With the exception of the distal portion of the neural spine, the 

 metapoph5^ses, the transverse processes, and a portion of the right 

 side of the anterior epiplwsis, this caudal (pi. 15, fig. 3) is in a fair 



