26 THE GENETIC RELATIONS OF THE CETACEANS. 
As to the forms most generalized, serious doubts may be enter- 
tained. The Denticetes have almost universally been considered 
as entitled to that rank, and if the form of the jaws and the 
teeth are alone considered, such would seem to be undoubtedly 
the correct view. But in other respects (such e.g. as the rela- 
tions of the bones around the calvarium, the frontals, the posterior 
portion of the maxillaries, the development of the lachrymal, the 
less atrophy of the pelvis, the rudimentary hind limbs) the Mys- 
ticetes appear to me to be the most generalized, and, although the 
evidence may be vague and inconclusive, I may be permitted, till 
contrary evidence supervenes, to represent such apparent proba- 
bility in a genealogical system. Of the two families (Balenop- 
teride and Balenide) known, the Balænids appear to have super- 
added to the Mysticete type the most specialized feature and most 
generalized characters, such, for example, as the orbital prolonga- 
tions of the frontal bones, the reduced coronoid processes of the 
lower jaw, ete. 
Denticetes. Respecting the families of Denticetes the evidence 
is also vague, but hints are furnished by various structural char- 
acters. These may be illusive, but in default of evidence to the 
contrary, and until superseded, may be followed. It may be that 
other parts would furnish conflicting testimony, that there may be 
an unusual persistence of primitive characters in some regions, 
while in some others the structure has been much modified, and it 
is even not impossible that there may have been a reversion to 
ancestral characteristics in certain parts, but until such devia- 
tions are proved, it seems most in accord with sound philosophy 
to take provisionally, and in default of other, the prima facie 
evidence offered. With these remarks, the succession of the vari- 
ous families of Denticetes may be sought. 
_ In the first place, two forms present themselves, each of which 
presents claims for the nearest representation of the ancestral line 
—the Iniids and the Ziphiids. The Iniids, and their near relatives 
the Platanistids, offer in their comparatively long neck and free 
_ vertebrae testimony in favor of such title, while the Ziphiids, in 
the development and continued independence of the lachrymal 
bones, produce theirs. And it seems very much more credible 
‘that these characters should have been inherited without fault 
ae than that they should have been the result of reversion after once 
au de! ea lost, especially as there appear to be no offsets to such 
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