PROFESSOR OWEN ON THE GENUS DINORNIS. 259 



Vertebra. (Plates XVIII. & XVIII a.) 



Of the five vertebrae in the present collection, only one is of a size which surpasses 

 in a marked degree that of the corresponding vertebra in a full-grown Ostrich ; but 

 all present much stronger proportions, especially of the spinous process, which is un- 

 usually robust. The largest vertebra', u I, is a cervical one, probably from below the 

 middle of the neck, anterior to those which are distinguished by a median inferior spine. 



The following are its dimensions as compared with the twelfth cervical of a full-sized 



Ostrich : — 



Dinomis. Strut hio. 



In. Lin. In. Lin. 



Length, at the middle of the terminal articular surfaces .29 22 



Breadth, at the middle of the body 16 8 



Height of the middle of the body 11 8 



Height from anterior base of spine to the lower part of the 



anterior articular surface 18 1 



Length of the neural arch 19 1 5 



Breadth of do 17 Oil 



Every process and prominence of this specimen of the vertebrie of the Dinornis is 

 broken off, with the exception of the right posterior oblique process. The texture every- 

 where presents large reticulate canceUi, which communicate with the outer surface by 

 an orifice on each side the neural arch, behind the upper transverse process. 



The body of the vertebra is square-shaped, with a broad and flat, or slightly concave 

 under surface : the anterior part of this surface is divided from the anterior articular 

 surface by a transverse channel, that surface being raised to a higher level. This 

 structure does not exist in the corresponding vertebrae of the Ostrich : it is slightly 

 indicated in those of the Apteryx. The spinal canal presents the usual infundibular 

 expansion at both extremities : it is not larger at its middle contracted part than in the 

 Ostrich. The remains of the base of the spinous process show this to have been almost 

 square- shaped, and much thicker relatively as well as absolutely than in the Ostrich. 



Two other vertebrae belong to the base of the neck, and correspond with those few 

 cervical vertebrae at that part which, in most birds, have a median inferior process for 

 the more advantageous origin of the great longus colli anticus muscle'. These two ver- 

 tebree must have come from the same or from closely contiguous parts of the neck ; but 

 they present differences of configuration and proportion which are incompatible with 

 the identity of the species of Dinornis to which they respectively belonged. 



Both manifest the generic massive proportions, the squareness of the body, the great 



' PLXVIII. figs. 1, 2, 3. 



' None of the cervical vertebrse present this character in the Ostrich or Emeu, but we find it in the last 

 cervical of the Rhea, and in the last three cervicals of the Apteryx and Bustard. 

 VOL. III. PART III. 2 H 



