MR. W. H. FLOWEE ON THE OSTEOLOGY OF THE SPERM-WHALE. 



331 



Platanista, and, unlike these, has no smooth articular facet on its hinder and upper 

 surface. 



There remain now to be described only the lateral processes, which constitute a very 

 peculiar feature in the bone. In all other Cetaceans the transverse processes of the 

 atlas, whether coniluent or not with those of the axis, bear but a small proportion in 

 vertical height to the whole bone, but appear as more or less conical (generally 

 obliquely flattened) projections arising opposite to the middle portion of the articular 

 surface, or, as in Hyperoodmi, from near the lower edge. In the Cachalot they form 

 two short, but very deep, vertically placed crests, rising as high as the top of the 

 neural arch, and extending below almost to the level of the inferior edge of the 

 condylar articular surface. At the ends they are obliquely truncated, being longer at 

 the lower than the upper angles. The middle of the posterior surface near the outer 

 edge is hollowed. The external margin seen from the side appears thicker below than 

 above ; it is rough and nodulated, especially near the inferior angle, being probably 

 not completely ossified. It will be observed in the annexed table of dimensions that, 

 although the atlas of the Caithness Whale is in all other respects somewhat larger 

 than that of the Tasmanian, the lateral development of the transverse processes is not so 

 great. This is chiefly due to their being vertically truncated, without any production of 



the inferior angle. 



Dimensions of the Atlas*. 



* My friend Mr. J. W. Clark, Superintendent of the Cambridge Anatomical Museum, has kindly given me a 

 drawing of the atlas of a young Cachalot, stranded at Hartlepool more than two centuries ago, and which is now 

 preserved, with other bones of the same animal, in the crjrpt beneath the library of the Cathedral at Durham. 

 The extreme width of this atlas is 29", its height 15". A comparison of this specimen with that of the Tasma- 

 nian and Caithness Cachalots, as representing three different ages, shows that the principal change which takes 

 place is the gradual contraction of the lower part of the central opening, that part, below the true neural canal 

 which corresponds to the odontoid surface of the axis. 



