140 ODOXTORNITHES. 



The Twenty-first Vertebra. (Plate XXII, figure 4.) 



A vertebra in the type specimen (number 1450) may be compared 

 with the twenty-first of Sterna regia. The centrum is somewhat crushed, 

 but appears to have been moderately broad below, and destitute of any 

 hypapophysis. It is deeply excavated at the sides, as are the other 

 dorsals, at least those from the posterior part of the series. The articulation 

 for the head of the rib is obliquely oval. The diapophyses as well as 

 the neural spine are broken off ; and the zygapophyses are crushed out of 

 position, but were approximate laterally, as in the preceding vertebrse. 



A vertebra (number 1732) adherent to the anterior end of the sacrum, 

 and almost wholly in front of the ilia, thus corresponding with the twenty- 

 first vertebra of the Tern, is also exposed in the matrix with that above 

 described. The neural spine appears to have been developed much as in 

 the Tern, but is here crushed. The diapophyses are broad, and at the 

 end were united to those adjoining by flattened ossified tendons. The 

 pre-zygapophyses look obliquely inward, and upward. 



The following measurements give the size of the twenty-first vertebra 

 in the type specimen of IcMhyomis dispar : 



Measurements of Twenty-first Vertebra. (No. 1450.) 



Length of centrum, 6.0 mm 



Least diameter of centrum, 1.5 



Vertical diameter of anterior articulation of centrum, 2.5 



Transverse diameter of anterior articulation of centrum, 3.0 



Vertical diameter of posterior articulation of centrum, 2.4 



Transverse diameter of posterior articulation of centrum, 2.5 



Transverse diameter of vertebra, across pre-zygapophyses, 3.0 



Transverse diameter of vertebra, across post-zygapophyses, 2.5 



