PEOFESSOR OWEN ON CNEMIOENIS. 261 



Besides size, the chief difference is in the greater relative breadth of the entire 

 vertebra, and more especially of the neural arch (as shown in fig. 3, pi. 63. torn. cit.). 

 This breadth is due in the anterior fourth of the cervical region to a diapophysial ridge 

 extending from the side of the prse- to that of the postzygapophj'sis, near which the 

 ridge (ib. fig. 1, a) stands out furthest, and has its margin thickened and roughened for 

 tendinous attachment. In the middle third of the cervical region the diapophysis 

 loses in antero-posterior extent of origin, but gains in length, or outstanding, and in 

 greater thickness of its free border for muscular attachment. The eighth cervical, for 

 example, is here 2\ inches in breadth. The outer surface of the base of the anchylosed 

 cervical rib is strongly sculptured by irregular longitudinal ridges and furrows. 



No Anserine comes near to Cnemiornis in this respect. Its cervical vertebrae recall 

 the proportions of those in Megaceros, and have a like relation to the muscular powers 

 brought to bear upon the head. In the extinct Anserine this probably related to the 

 gripe and tug exercised by the broad, short, but strong beak upon the vegetable growths 

 torn up for food. 



The third cervical (ib. fig. 1), like the fourth, is broader than it is long. The hyp- 

 apophysis is represented by a sharp ridge, 8 lines in length, at the hinder half of the 

 centrum, terminating in a short tuberosity (ib. hy) projecting beyond the hinder 

 articular facet. The parapophysial plate extends from the lower angle of the anterior 

 articular surface of the centrum to the hinder half of that element, ascending upon its 

 side, and forming the floor (ib. ^j) of a vertebrarterial canal, 10 lines in length, and 

 8 lines in diameter at the hinder outlet (v). The end of the rib-element (ib. pi) 

 forming the outer wall of the canal is broken off. In the fourth cervical the neural 

 spine is entire; it is also short and rounded, as in the third (fig. 1, ns); and more of 

 the pleurapophysis is preserved. The hypapophysis has its base shortened to an extent 

 of 5 lines ; but its apex extends downwards, 3 lines below the hinder articular facet 

 (h, fig. 2, pi. 63, torn. cit.). 



The side view of the twelfth cervical vertebra (ib. fig. 6) shows the division of the 

 hinder part of the vertebrarterial canal into two foramina (ib. v, v') by the bony bar 

 passing from the pleurapophysial plate backward and downward to the lower part 

 of the side of the centrum. In Cereopsis (ib. fig. 9) and Tachjeres (ib. fig. 10) the 

 vertebrarterial canal of the answerable vertebra has also two hinder outlets {v & v') ; but 

 the dividino' bar passes from the hind border of the rib-plate upward to coalesce with 

 the neural arch, and the upper outlet (y') is much less than the lower one {v). The 

 diapophysis (ib. fig. 6, d) projects freely, in Cnemiornis, above the longitudinal ridges : 

 these alone mark the rib-prominence below the preezygapophysis in Cereopsis (ib.fig. 9) 

 and Tachyeres (ib. fig. 10). 



The vertebree bearing freely-movable ribs are nine in number in Cnemiornis, of which 

 the last three are anchylosed with the sacral mass. The rib of the first dorsal is free at 

 the distal end ; the centrum has a hypapophysial tuberosity at its fore part, the size of 

 VOL. IX. — PART ni. May, 1875. - ^' 



