1882. | * SPECIES OF HYPEROODON, 395 
the ‘‘infraorbital ”? foramina are smaller—a character probably related 
to the smaller surface-region to be supplied by the nerves and vessels 
which pass through it, occasioned by the reduced size of the crests and 
a possibly shorter rostram,—and that the temporal fossa is shorter 
from before backwards, and higher vertically, more resembling that 
of Ziphius cavirostris. 
There is little, in such portions of the under surface of the skull 
as are preserved, that shows any striking difference from the common 
species. 
A sufficient portion of the vomer is preserved to show that it was 
not complicated by the adherence to it of an ossified medio-rostral 
bone, in which respect it agrees with all known specimens of Hy- 
peroodon and Berardius, and differs from the adults of Ziphius and 
Mesoplodon. 
Owing to the destruction of some of the more prominent of the 
external parts of the cranium, very few dimensions can be given 
beyond those at p. 393; but the following comparisons may be 
useful :— 
HT. planifrons. H. rostratus. 
millim, millim. 
Width between anteorbital notches........ 432 385 
Width of base of each maxillary crest oppo- 
site anteorbital notches..............0% 160 127 
Interval between crests......6..0.000 0005 105 130 
As the cranium thus differs from that of H. rostratus in the com- 
parative lowness and rounded form of the maxillary crests, from ZH. la- 
- tifrons (with its enormous, vertically raised, flat-topped and con- 
verging crests) it deviates in a so much more marked degree that a 
detailed comparison between them is quite unnecessary}, 
With so imperfect a knowledge even of the cranium, and with 
absolutely none of the remainder of the animal’s organization, any 
determination of its generic affinities can only be provisional ; but if 
the genus Hyperoodon include both H. rostratus and H.latifrons, 
there is no reason against this new form being contained in it also. 
If, on the other hand, they are separated, as was done by the late 
Dr. Gray, it would have to form a distinct genus, as it differs quite 
as much, or more, from H. rostratus in one direction as H. latifrons 
(Lagenocetus latifrons of Gray) does in the other. Not wishing 
to multiply genera, I prefer the former course, and shall consider it 
a Hyperoodon; and as it differs from both of the other species in the 
comparative flatness of the fore part of the head (which looks ex- 
ternally like, although not strictly homologous with, the animal’s 
forehead), it may be specifically called planifrons. It is evidently 
1 H. latifrons is considered by some zoologists to be the adult male of . ros- 
tratus, Captain David Gray, of Peterhead, who is perfectly familiar with both 
forms, has furnished me with some evidence strongly tending to the opposite 
conclusion. I hope, with further information from the same source to be col- 
lected during the present whaling-season, to be soon in a position to clear up 
this important and still doubtful question in cetology. 
