The chief differences between the Barnegat City and Newport skeletons are
in the size and form of the processes of the cervical vertebræ, the form
of the seventh and eighth thoracic vertebræ and of the ribs connected
with them, the direction of the acromion of the scapula, the shape of the
first phalange of the first digit, and of the posterior segments of the
sternum. As far as the processes of the cervicals are concerned, these
are known to be extremely variable in all cetaceans. The seventh and
eighth thoracic vertebræ are those on which the mode of attachment of the
ribs changes in ziphioid whales, and I have observed in the genus
_Mesoplodon,_ as here, that the processes and articular facets were very
variable, being sometimes quite unlike on the two sides of the same
vertebra. The direction of the acromion is probably subject to large
individual variations, though this can not be determined at present, and
the same is true of the form of the first phalange of the first digit.
The form of the sternum is quite variable in all cetaceans, and can not
be relied on for specific characters, without comparison of many
individuals.
On the whole, I am of the opinion, as already stated, that we are not
compelled by the differences noted to regard the Barnegat and Newport
skeletons as representing different species. The Charleston skeleton is
too young and imperfect to admit of serious consideration. The idea that
the differences between the adult skeletons are probably individual
receives support from the fact that the skeleton shown in the photograph
from St. Simon Island, Georgia, mentioned on page 31, No. 14, appears to
possess a combination of characters exhibited by the other two.