206 PROFESSOE FLOWER ON THE EECBNT ZIPHIOID WHALES. 



It must be premised that as far as is at present known, putting aside the peculiar 

 rounded form of the head in Hyperoodon, the external characters of the various known 

 Ziphiinffi afford no grounds for generic subdivision. It is to the skeleton and the teeth 

 that we must look in examining whether the group is truly homogeneous or not ; and it 

 is only very recently that complete skeletons of a sufficient number of individuals have 

 been knowTi, to attempt a comparison between them. The teeth have been relied upon 

 almost entirely ; and I agree with Professor Owen that the trifling diflierences in the 

 situation of the developed teeth are not such as, unless accompanied by other more 

 important and constant characters, are sufficient for generic distinction; but, at the 

 same time, if such differences are constantly associated with others, they may be useful 

 guides to classification. 



HyPEKOODON (Lacepede) appears to difier from all the other Ziphiinae in the cha- 

 racters of the cervical vertebrae, especially in their great antero-posterior compression, 

 the constant ankylosis of all seven, and the absence of inferior transverse processes 

 in the third, fourth, fifth, and sixth ^; it has also only nine pairs of ribs, and but forty- 

 five vertebrae in alP. In the more essential characters of the cranium it resembles one 

 of the other sections to be spoken of presently [Mesoplodon), with the superaddition of 

 the great maxillary crests ; and in the dentition it resembles more nearly another 

 section {Ziphius). 



Having separated Hyperoodon, the remaining known members of the subfamily agree 

 in having a comparatively well-developed cervical region, with certain of the posterior 

 vertebrae (one, or usually more) permanently detached, and with distinct inferior 

 transverse processes as far as the sixth, in having almost always ten pairs of ribs^ 

 and at least forty-six vertebi-ae, usually forty-eight or forty-nine. There are, however, 

 in the conformation of the skull and the form and situation of the teeth considerable 

 differences, by which they may be divided into three distinct sections, which appear to 

 me to be natural, and which are not, as far as is yet known, united by intermediate 

 forms ; so I think that they may well be considered generic, though of course this is 

 a subject upon which the judgment of zoologist may differ. I can see no grounds 

 at present for any further subdivision. 



These sections may be characterized as follows — though the distinctive peculiarities 

 are more readily appreciated by an inspection of a specimen than they can be expressed 

 in words. 



' The great differences between the cervical vertebra; of Hyperoodon and Ziphins cavirostris (erroneously 

 called Hijperoodon gervaisti) were ijointed out by Duvernoy (Annales des Sciences Naturelles, 1851, p. 24). 



^ The animal described by Cope, apparently without personal examination, as Hyperoodon semijunctus (Proo, 

 Acad. Nat. Sc. Philadelphia, 1865, p. 280), and stated to be in the Charleston Museum, is evidently not a 

 Hyperoodon, but most probably a trae Zipliim. It was but between twelve and thirteen feet long, has the 

 four posterior cervical vertebra; fi-ee, has ten pairs of ribs, and two more vertebrae than Hyperoodon. 



' The skeleton of Ziphius cavirostris at Jena has but nine pairs of ribs. 



