PRESACRAL VERTEBRAE OF ICIITHYORNIS. 139 



The Nineteenth Vertebra. 

 The succeeding vertebra in the above series (number 1732) is some- 

 what crushed laterally, so that the centrum appears keeled, but it was 

 probably rounded below. At the sides, it is excavated, leaving only a 

 thin median wall. The diapophyses are strong, nearly horizontal, and 

 directed somewhat backward. They are supported by a vertical ridge 

 below, and bear at the end a small sub-circular articular face for the 

 tubercle of the rib. Their upper surfaces are moderately broad. The 

 neural spine is as extensive at its thickened upper end as the centrum. 



A vertebra not figured, which may be reg-arded as the nineteenth, is 

 represented in one specimen (number 1733) by less than half of a centrum, 

 apparently the posterior end, which has a nearly circular and slightly 

 concave articular face. This centrum is broken near the middle, showing 

 a transverse section very similar in form to that of a T rail inverted. 

 A similar section might be made across the centra of the three preceding, 

 vertebras of this species (Ichthjornis victor.) 



The Twentieth Vertebra. 

 Another more posterior vertebra not figured, belonging to this specimen 

 (number 1733), has a shorter and stouter centrum than the preceding, and 

 is less excavated at the sides. The articular surfaces are concave. The 

 parapophysial surface for the head of the rib is small, and elevated. The 

 neural canal is much crushed, and the zygapophyses, diapophyses, and 

 neural spine, are broken away. 



The twentieth vertebra of number 1732 is broader below than the 

 nineteenth, and rounded, without trace of hypapophysis, The sides of the 

 centrum are excavated above the middle, and the articular faces are sub- 

 circular, and moderately concave. 



The diapophyses are strong, and supported by a ridge below. They 

 are directed somewhat backward, and terminated by a small face for the 

 articulation of the tubercle of the rib. 



