424 MR. W. H. FLOWER ON A NEW [Nov. 8, 
With the exception of the two anterior and the posterior, they are of 
very nearly equal size throughout. Their number is the same in 
both skulls, viz. eight on each side above, and ten below; but though 
the whole number is the same, I suspect that it is not exactly the 
corresponding teeth which are in place in both specimens, at all 
events as far as the upper jaw is concerned. By comparing tooth 
with tooth, especially as regards their position in the alveolar margin, 
the older specimen would appear to have lost the small anterior pair 
present in the younger one; while in the latter the posterior pair 
appear not yet to have been developed. It must be confessed that 
our knowledge of the growth and succession of these organs in the 
Cetacea is at present so imperfect that we ought not to lay much 
stress upon any trifling variations in their number or character in 
discriminating species. 
The only other species of Orca from the southern hemisphere 
hitherto known is O. eapensis, Gray, an animal closely allied to, indeed 
by some naturalists thought to be identical with O. gladiator, the 
common Killer or Grampus of our seas. The principal differences 
between the Tasmanian skull and that of O. capensis are the fol- 
lowing :—Its size is much smaller, measuring in entire length but 
23 instead of 38 inches. The brain-cavity is relatively very much 
larger, and the outer surface of the eranium comparatively smooth. 
In O. capensis the ridges for the attachment of the muscles are 
enormously developed, and conceal the form of the brain-case. These 
differences, being those that are found between young and old indi- 
viduals of the same species, might at first sight give rise to the idea 
that such a relationship existed between the two skulls under com- 
parison, were it not for the signs of maturity possessed by the smaller 
skull, and did we not also know that a similar relation exists between 
the small and large species of all natural groups. But, in addition 
to these, in the Tasmanian skull the nasals are larger, and the pre- 
frontal does not rise in front of them to the vertex of the head, as 
in O. capensis. A great difference is also seen in the form of the 
premaxillaries: in the new specimen these bones are widest at the 
middle of the beak, their outer border at this part being convex, 
approaching in the amount of their encroachment upon the maxil- 
laries those of the genera Grampus and Globiocephalus ; while in the 
large Cape species they are very narrow at the middle of the beak, 
and dilate towards their anterior termination, the outer border being 
eoncave. ‘The form of the palate is generally the same; but it is 
rather more contracted behind the last tooth, and the tooth-line is 
rather less curved, than in O. capensis. The teeth are fewer in 
number, more regularly conical, less compressed in the antero-poste- 
rior direction. In the lower jaw the symphysis is proportionately 
longer, more shallow and sloping. As O. gladiator agrees with O. 
capensis in all the above-named points, the present species is distinctly 
differentiated by its cranial characteristics from the two large mem- 
bers of the genus. 
In the ‘ Zoology of the Erebus and Terror,’ Dr. Gray has figured 
and described a skull (in the British Museum, locality unknown) 
