314 ME. W. H. FLOWER ON THE OSTEOLOGY OF THE SPEEM-WHALE. 



column, and insufficient spaces left between the bones ; so that even these measurements 

 afford but an approximative comparison. 



Cranium. 



In no kno^vn mammal does the cranium depart from the ordinary type to such an 

 extent as in the Cachalot. The expansion, elongation, flattening, and distortion of 

 many of the cranial and facial bones, met with in a certain degree in all Cetaceans, is 

 here carried so far as to render it by no means easy, at least in the adult animal, to 

 recognize their homologies. Comparison with the skulls of young individuals and of 

 less-modified cetacean forms, however, clear up most of the apparent difficulties. 



The size of the skull in the adult animal is larger in proportion to the remainder of 

 the body than in any other known mammal *. As in all animals in which the great 

 bulk of the skull is made up of the face and jaws and not of the brain-case, the rela- 

 tive size of the entire head increases with age, at all events up to maturity ; and it is 

 probable that the jaws continue to augment in size and weight after the growth of most 

 other osseous structures has ceased. The relative length of the cranium to the vertebral 

 column (the vertebrae being placed in contact) in the Sydney skeleton (according to 

 Wall) is as 46 to 100, in the Tasmanian as 57, in the Caithness as CO, and in the York- 

 shire as 67 to 100. The first is scarcely more than half-grown, the second adolescent, 

 the last two adult. 



As seen in the section, PI. LVI. fig. 1, the cerebral cavity is of comparatively limited 

 dimensions, being of a somewhat spherical form, with an average diameter of about 10", 

 and a capacity of 900 cubic inches. In front of this stretch out horizontally the 

 enormously developed bones of the upper jaw, to which the great size of the entire skull 

 is mainly due ; while rising above it is the high, compressed, vertical, transverse wall 

 of bone forming the great occipital crest, the posterior boundary of the enormous 

 supracranial basin, so remarkable a feature in this singular skull. 



The general form of the cranium may be compared to that of a huge pointed slipper, 

 with a high heel-piece, and the front part trodden down. The lower surface is remark- 

 ably straight and flat, though sloping upwards at the sides. The outline, seen from 

 above, is long and narrow, rounded behind, maintaining a tolerably uniform breadth for 

 the posterior two-thirds of its length, and acutely pointed at the anterior extremity. 

 The upper surface is, except quite in front, concave, the vast hollow in which the so- 

 called " head-matter " of the whalers (composed of nearly pure spermaceti) lies being 

 limited behind by the occipital crest, continued laterally into the elevated edges of 

 the broadly expanded maxillae, which rise from the median line towards the margin of 

 the skull, instead of falling away as in most Cetaceans. The great breadth of these 

 bones in front of the antorbital notch takes away the appearance of a distinct rostrum 

 or beak, generally characteristic of the long-snouted dolphins. 



* The skxUl of BalcBiia mystketus is rather longer in proportion to the vertebral column, but it is less massive. 



