PROF. W. H. FLOWER ON THE GENUS MESOPLODON. 421 
young animal and in all other species of Cetacea. The median ossicle in the snout 
of the Pig offers a similar case of an independent ossification in the anterior extremity 
of the mesethmoid cartilage. 
The skull, as seen from above (Plate LXXI. fig. 1), presents several characters by 
which it can be readily distinguished from M. didens and the closely allied MV. CuropeUus. 
The principal of these is the sudden narrowing of its outline at the commencement 
of the rostrum, due to the presence of the deep lateral groove mentioned above. In 
the British species the rostrum is wider at the base, and passes more insensibly into the 
cranium. The next point is the relative position of the premaxillary ( pf’) and the maxil- 
lary (mf') infraorbital foramina—the former being behind the latter in the southern, 
and on the same level in the northern species. The third is the form of the premaxille, 
which are more expanded and flattened out (especially the right) immediately in front 
of the narial apertures in WV. australis. In the conformation of the upper ends of 
the premaxille and of the nasal bones the differences are but slight. 
M. layardi, as mentioned above, agrees with the northern species in the disposition 
of the infraorbital foramina, and the absence of any marked lateral basirostral groove ; 
and by these as well as by its very characteristic dental characters it is distinguished 
from the one now under consideration. V/. densirostris is much more closely allied to 
our new species, having (judging by the figure in Van Beneden and Gervyais’s Ostéo- 
graphie, pl. xxv.) a very similar outline as seen from above. It differs, however, 
independently of the mandibular and dental characters, in the far more massive rostrum, 
which, although no longer, has exactly double the vertical height at the middle, as seen 
in the profile view of the skull. 
A marked difference is also seen‘on the lower surface of the skull. In WV. densi- 
rostris the palate-bones completely surround the anterior pointed ends of the pterygoids, 
widely separating the latter from the maxillaries ; while in 1. australis the palatines 
on the inferior surface of the skull lie altogether on the outer side of the pterygoids, 
and do not even extend so far forwards as the pointed extremities of those bones, 
which thus by their free end and inner side come into direct contact with the 
maxillaries. 
It remains only to compare this skull with the other New-Zealand forms—the 
typical IZ. grayi of Haast, the rostrum which I propose to call MZ. haasti, and M. hectori. 
With the former it has very near affinities—so much so, that from an examination 
of the cranium alone I should scarcely think of placing them in different species. 
It is needless to dwell upon differential characters which may be merely individual ; 
but I may indicate the following as perhaps of more importance. a. Size: MW. australis 
would appear to be smaller than IZ. grayi. The two complete skulls are practically of the 
same size; but that of the former is adult and that of the latter young, and the tympanic 
bone of the latter is slightly larger than that of the former. Dr. Haast gives 17! 6" 
as the length of an adult female of IZ. grayi, whereas the adult MW. australis (sex not 
