No. 406.) . DINOSAUR-AVIAN STEM. 787 
* cervico-dorsals" of the Sauropoda and those of the emeu 
(Dromzeus), as follows: ** The long neck, similar in structure 
and almost as flexible as that of an emeu (Dromeeus), could 
thus pass through a prodigious arc in the search for food, 
either under or above water. The neck motion partly involved 
the anterior non-spine-bearing dorsals (vertebrae with free ribs, 
equivalent to the *cervico-dorsals' of birds), as in Dromzeus, 
behind which the comparatively inflexible, large, spine-bearing 
dorsals rose to maximum height in the sacrum for the inser- 
Fic. 6. — Neck of bird (Dromzus). Cervicals 13-14 and cervico-dorsals 1-2 E lacking 
median spines; dorsal 3 with a large blunt in spine. After Osborn 
tion of the Zgamentum nuche and elevator muscles." 
The importance of such an hypothesis of function will appear 
in the following description and discussion, and it applies to 
all the Cetiosauria, namely, to the Morosaurus and Diplodocus 
types as well, which, so far as known, are uniform with the 
camarasaur type in the peculiar bird-like arrangement of the 
posterior cervicals and anterior dorsals. (See Fig. 7.) 
Again, in the description of Diplodocus, Osborn (99 (1), 
p. 200) pointed out the resemblances in the relations of the 
posterior ribs to those of Apteryx. Two features were brought 
out, namely: two of the ribs actually underlie the anterior 
