ON THE CAUDAL VERTEBRA OP A CETACEAN. 



709 



interest, affording, as it does, such an important confirmation of the 

 conclusion that a great change in the physical conditions of the area 

 must have occurred at the time when these marine strata were 

 deposited. 



APPENDIX. 



Note on the Caudal Vertebra of a Cetacean discovered by Prof. 

 Judd in the Brockenhurst beds, indicative of a new Type allied 

 to Bal-enoptera (Balcenoptera Juddi). By Prof. H. G. Seeley, 

 F.R.S., P.G.S. 



The vertebra submitted to me by Professor Judd belongs to the 

 caudal region ; and although in a new type there may be some doubt 

 concerning the exact place in the series, it may be affirmed to have 

 been about the eighth caudal, and certainly not later than the 

 twelfth. The vertebra is probably distinct from all recent and 

 fossil genera ; but its characters are altogether in harmony with the 

 BalaBnidse ; and the specimen indicates a genus much more closely re- 

 lated to Balcenoptera than to Balcena, so far as can be judged from 

 a single vertebra. This affinity is especially shown in the character 

 of the base of the centrum, which had the facets for the chevron 

 bones very small, and also in the general character of the neural 

 arch, which is much less massive than in Balcena. The differences 

 from the gveai Balcenoptera musculus on the other hand are clearly de- 

 fined, and appear to consist in the remarkably forward position of the 

 neural arch (fig. 2), since in Balcenoptera it does not usually reach the 

 anterior sutural margin. The depressed transversely ovate outline of 

 the neural canal (fig. 3) is another distinctive character, since in Ba Ice- 

 noptera the neural canal is higher than wide. The neural spine also 

 appears to be much less developed than in the recent genus, though, 

 as the hinder part of the neural arch is broken away, this character 

 cannot be positively affirmed. The centrum is relatively much shorter 

 (fig. 2) ; the facets and ridges on the base connected with the chevron 

 bones are less developed. The transverse width of the zygapophyses 

 was relatively greater in the fossil. The transverse process is re- 

 markable for extending the entire width of the centrum (fig. 2), and 

 for having the vertical perforation rather behind the middle of the 

 centrum (fig. 1), since in Balcenoptera it is placed further forward. 

 Balcenoptera laticeps, however, a species of the North Sea, ranging, 

 perhaps, to Java and Japan, approaches nearer to the fossil, espe- 

 cially in having the epiphyses separate ; the neural arch, too, is 

 placed almost as far forward as in the fossil, but is higher, and the 

 neural spine is larger ; but otherwise its characters are very similar. 

 Perhaps when we reflect that the contemporaries of this old whale 

 were Palceoiherium, Anoplotherium, and their allies and congeners, 

 all of which have passed away, it will not seem improbable that the 

 marine mammals also should give evidence of subgeneric differences, 



