OCR Text |
Show 1882.] SPECIKS 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 rostrum,-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 Hyperoodon 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:- H planifrons. H. rostratus. millim. millim. Width between anteorbital notches 432 385 Width of base of each maxillary crest opposite anteorbital notches 160 127 Interval between crests 105 130 As the cranium thus differs from that of H. rostratus in the comparative lowness and rounded form of the maxillary crests, from H. latifrons (with its enormous, vertically raised, flat-topped and converging 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 externally 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 H. rostratus. Captain David Gray, of Peterhead, w ho is perfectly familiar with both forms, has furnished m e with some evidence strongly tending to the opposite conclusion. I hope, with further information from the same source to be collected during the present whaling-season, to be soon in a position to clear up this important and still doubtful question in cetology. |