ME. W. H. FLOWER ON THE OSTEOLOGY OE THE SPEEM-WHALE. 



323 



Many of the differences of the skull, dependent upon age, are well illustrated in 

 PI. LVI., where drawings of median sections of the crania of the young and adult 

 Tasmanian Cachalots are given on the same scale. Extraordinary as the disproportion 

 of the facial part of the skull to the cerebral ca^'ity appears in the older skull here 

 figured, a drawing of tlie Yorkshire specimen would show the same character in an 

 even more exaggerated degree. 



In the same Plate a figure of the section of the cranium of a Hyperoodon has been 

 introduced, as that of the Whale which (except Eogia) approaches most nearly in its 

 general characters to Physeter. It is easy to see, by this section, how those fantastic 

 and apparently meaningless developments of the cranial bones of Hyperoodon and the 

 Ziphioid Cetaceans may become, with little modification, the regular and definitely dis- 

 posed walls of the huge spermaceti-basin of the Cachalot. The crest, essentially the 

 same in both, is merely flattened out and expanded, as if by pressure from within ; and 

 the great maxillary protuberances are reduced in size. The most essential differences 

 between the cranium of Physeter and the Ziphioids are, as already pointed out, the 

 absence of a distinct lachrymal bone, and the construction of the zygomatic process of 

 the malar. 



Loioer Jaw. 

 Perhaps no part of the skeleton of the Cachalot is so well known as the lower jaw, 

 as few Museums of note do not possess one or more of these tangible trophies of a 



* Owing to the imperfect condition of this skiiU, the dimensions given cannot be relied on as quite accurate. 



