158 PROFESSOR OWEN ON THE GENUS DINORNIS. 



figures 34 and 39 of Mivart, which show the same aspect (haemal or ventral) of the 

 vertebrse compared. And here I may note that the processes seen in profile in 

 Mivart's figures 33 and 34 are indicated by the symbol c in the sixteenth vertebra, and 

 by the symbol hj in the seventeenth ; similarly, they are described as ' catapophjses ' at 

 p. 405, and ' hijpapophyses ' at p. 406. I note them, under the latter denomination, in 

 tlie thirteenth as in the fourteenth vertebra of Binornis maximus, and the similarity is 

 such between these vertebrte that I proceed to the description of the fourteenth. 



In the fourteenth cervical (fig. 17) the more approximated hypapophyses, hy, arise 

 from a low common prominence further back from the preaxial surface, and the lon- 

 gitudinal channel in the lower surface, in the twelfth and thirteenth vertebrte, is here 

 somewhat interrupted by such prominence. The transition of these into a single medial 

 hypapophysis is thus indicated. The present vertebra in Binornis maximus approaches 

 the character of the seventeenth vertebra in the Ostrich i, especially in the above 

 modification of the hasmal surfiice 2, to which view of the vertebra of Biiiornis maximus, 

 corresponding to the seventeenth of Struthio, I here restrict my illustrations of such 

 vertebra. 



The processes (c in Mivart's fig. 34, hy in his figure 39) are serial homotypes. The 

 recognition of this fact led me to speak of Mivart's ' catapophyses ' as " parial hypa- 

 pophyses " in the Memoir on Cnemiornis (Trans. Zool. Soc. ix. p. 260), and again, under 

 a sense of the convenience of a substantive term, as ' praehypapophyses ' (ib. ib.), in 

 contradistinction with the ' hypapophyses ' at the hind part of the centrum in the axis 

 and third cervical. The antero-posterior extent of the pleurapophysial plate is 

 shortened in the fourteenth vertebra of Binornis, as in the seventeenth of Struthio ; but 

 the pleurapophysis itself is less produced in Binornis. The neural spines have not 

 approximated and coalesced as "in Struthio. The section of the supporting column of 

 the parial neural spines is transversely quadrate; both fore and hind surfaces are 

 impressed by a definite rough tract for the elastic ligaments. The preaxial surface 

 retains a greater relative breadth to the postaxial than in Struthio ; the vertebrarterial 

 canals are relatively wider. 



The next step in the transmutation of Mivart's ' catapophysis ' into the normally 

 situated single hypapophysis in birds is presented by the fifteenth cervical of Binornis 

 maximus (figs. 18-21), which is the last of that series in the present skeleton. 



A single obtuse process descends from a low base coextensive nearly with the 

 haemal surface of the centrum (fig. 19, hy) ; but the base of this process in one example 

 is connected by a ridge continued from each side to the hind border of the pleur- 

 apophysis (ib. pi), and there is a slight swelling (the final trace of the parial character) 

 at the beginning of each ridge. A pair of low tuberosities, connected by a ridge, mark 

 the hind border of the lower surface of the centrum. 



With the vertical extension of bone, hy, from this surface for muscular attachments, 



' Mivart, he. cit. p. 406, figs. 35-39. » Ib. ib. fig. 39. 



