MR. W. H. FLOWER 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 confluent 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 Hyperoodon, 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*. 
Tasmanian. | Caithness. 
in. in, 
HcieMeNPLEAC EEL. jeMtarreeetaLcin etniai eters vcs © chelacatie sores eleteine oe 37% 36 
Width between outer edges of anterior articular surfaces ...... 23 26 
Extreme width of each of these surfaces ...........-.00000ee 4 10 
Extreme height of each of these surfaces..............00ee08 144 163 
WWodth: of menralicariall wat ott vrrua sprain oe saree sors sere « 92 11 
Hetsht; ofneural canal. nersre syeiomiercieeiers cre piavateieiers vie oct eesyers  « 10 102 | 
Height of contracted lower portion of the canal .............. 4 25 
Width of contracted lower portion of the canal at the upper end. 32 1 
Contnactine BelowstOme sp isissicce tera ,cniever ne el es hs ccc eie 1 1 
Height of portion of bone below the neural canal ............ 64 74 
Hxiremeherpbiinimiddle ]ine 056 2c see eects wns ne os os 182 213 
Vertical height of transvérse processes at outer end .......... 14 
Greatest antero-posterior thickness of the same .............. 5 ; 
iHeieht onnenralarcommumiddle: 5) .n)ejs) ae aries «the ele celica ole <2 4 3h 
Antero-posterior thickness of neural arch in middle ..,....... 37 ae 
Length of inferior surface of bone in middle line............ 6 63 
Width between the outer edges of posterior articular facets .... 25 
* 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 erypt 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, 
