ie ee. | 
XII. On the Axial Skeleton of the Ostrich (Struthio camelus). 
By St. Groree Mrvart, F.R.S. 
Received June 18th, 1872. 
RECENT investigations having made it probable that the line of affinity between Birds 
and Reptiles passes through the Struthious members of the first of these classes, I have 
deemed it advisable to commence a study of the axial skeleton of the Sawropsida by a 
detailed examination of that of the Ostrich, as of the most generalized type. 
By kind permission of the authorities of the Royal College of Surgeons, I have been 
enabled to make use of the rich resources of that institution, not only for examination, 
but for the purposes of illustration, all the figures being from specimens in that 
Museum. 
Bearing in mind the varying posture which the axial skeleton assumes in different 
Sauropsidans, I think it better, generally, to employ the term preavial to denote that 
relation which in a vertical spinal column would be called “superior,” and in a hori- 
zontal one ‘‘ anterior.” Similarly I use the word postaxial for what under the circum- 
stances mentioned would be either “inferior” or “posterior.” In the same way the 
terms dorsal and ventral stand for “posterior” or “superior,” and for “anterior” or 
inferior ” respectively. 
After describing the various vertebre throughout the spine one after another, I pro- 
pose to describe the pelvis as a whole, then the vertebral and sternal ribs, and the stemum, 
concluding with a recapitulation of the serial modifications the several parts and pro- 
cesses undergo as we proceed postaxially from the atlas to the coccyx. 
There are seventeen cervical vertebre, which, in the adult, have either no rib-like 
processes or only styliform and anchylosed ones (fig. 1, c). 
The next three vertebree bear longer ribs, generally articulated movably with their 
vertebree and not directly connected with sternal ribs. They may be called cervico- 
dorsal vertebre (fig. 1, cD). 
The next five vertebra (twenty-first to twenty-fifth inclusive) support long ribs, which 
unite distally with sternal ribs articulated to the sternum, and are therefore true dorsal 
vertebre ; these vertebre do not anchylose together or with the sacrum (fig. 1, D). There 
are two vertebre after these (twenty-sixth and twenty-seventh) which bear freely-ending 
* ribs or rib-like processes, and which normally anchylose with the sacrum in the adult ; 
these can be distinguished as dorso-lumbar vertebre. Sometimes’ there may be an extra 
> As in the mounted skeleton in the Bird Gallery of the British Museum. 
VOL. VilI.—PaRt vil. March, 1874. 3T 
