CETACEA. 73 



bone Whale show the same difference ; but ihe head in both states 

 is smaller, compared with the entire length of the animal, than in 

 the northern or Greenland species. 



2. That the bones of the Whalebone Whales in the very young 

 state are the same in number, and nearly the same in form, as in 

 the adult animal, the bones only becoming more or less completely 

 ossified, which they appear to do very slowly, and in some species 

 even more slowly than in others ; so that the notion that the number 

 of vertebrae increases with the growth of the animal, which has been 

 entertained by some naturaUsts, is a mistake. 



3. It also appears that certain parts which become ossified in most 

 kinds of Whalebone Whales do not become so in others. Thus, the 

 lateral processes of the cervical vertebrae of Megaptera, Benedenia, 

 and Physalus seem to be nearly of the same form in the young and 

 cartilaginous state ; that is to say, they have the usual form of these 

 bones in the Balcenopteridce ; and though the entire lateral process 

 becomes ossified in Physalus and Sibbaldius, the end of the process 

 remains cartilaginous at least to a much greater age, if not always, 

 in the genera Megaptera and Benedenia. Naturalists observing this 

 apparently imperfect development of the bones in the latter genus, 

 have been induced to believe that it arose from the youth of the 

 specimens observed, instead of being a peculiarity of the genera, 

 overlooking the fact that the skeletons of the oldest Megapterce that 

 have been examined show the same apparently imperfect develop- 

 ment and truncated form of the bones. 



4. The general form of the baleen, the comparative thickness of 

 the enamel, and the fineness or coarseness of the internal fibres 

 which form the marginal fringe, and the internal structure as shown 

 by the microscope, aU present good characters for determining the 

 species and for separating the Whalebone Whales into natural 

 groups, as I have shown ia the ' Zoology of the Erebus and Terror.' 



The quahties of the whalebone or baleen from various localities, 

 and hence from dilferent kinds of Whales, have been observed, and 

 have led to their employment for difierent purposes by the handi- 

 craftsman ; according to their goodness and rarity, they fetch very 

 different prices in the market — an instance of the practical working 

 man and the trader being in advance of the scientific zoologist. 



5. The difference in form of the tympanic bones is great, and 

 affords good characters, not only to separate the species from one 

 another, but also to group them into families and genera. 



6. The fact that soine Whalebone Whales have the first rib fur- 

 nished with a double head, one head attached to the last cervical and 

 the other to the first dorsal vertebra, which had been observed by 

 Eudolphi, Yarrell, Dubar, and Schlegel, though apparently considered 

 as only to be found ia the young state of the species by the latter 

 author, disappearing as the animal increases in age, proves, I believe, 

 to be a permanent peculiarity of considerable importance, and justifies 

 Ijlljeborg in using it as a character for the discrimination of the 

 species, and even for separating the Whales into groups or genera. 

 That it is not a peculiarity of the young state is proved by its being 



