330 MR. W. H. FLOWER ON THE OSTEOLOGY OF THE SPERM-WHALE, 
In the Caithness Cachalot the inferior part of the opening is altogether smaller and 
especially constricted laterally, the sides being nearly parallel and 1” apart for a 
distance of 23”. 
The articular surfaces for the occipital condyles are broad and shallow, without any 
sharply defined projecting border, except at the superior internal angle. ‘They approach 
each other below, but do not meet by a space of about 2”. The bone between their 
inner margins and the edge of the neural canal is hollowed into several very rough 
irregular depressions, especially on the right side. 
The neural arch, arising on either side immediately above the condyles, is a nearly 
straight horizontal bar of bone, slightly thicker from before backwards than from above 
downwards. Its anterior is thicker than its posterior edge. It presents no appreciable 
spine, but, on the contrary, is rather hollowed than otherwise above. There is, how- 
ever, a slight rounded prominence on the middle of the anterior margin. In the 
Caithness specimen this is more developed, forming an irregular, low, tuberous spine. 
Posteriorly, on the right side, near the root of the arch, is a nearly circular flattened 
surface, 4” in diameter, with an irregular depression in the middle, and of which the 
edges are developed above and below beyond the surface of the bone from which it 
springs. This facet closely fits a corresponding one on the commencement of the arch 
of the axis. It is evidently irregular, no trace of it being present on the other side; 
but it is worthy of note that a similar articulating facet between the atlas and axis, in a 
corresponding situation, but on the opposite (left) side, exists in the Caithness specimen. 
The neural arch of many Cetaceans and of other Mammals is perforated laterally by 
a large foramen, through which the first cervical nerve finds a passage. In some, the 
part constituting the anterior wall of the foramen, and which joins the upper edge of 
the anterior articulating surface, is absent; and the foramen is then represented by 
a deep groove with more or less overhanging edges. In Hyperoodon the foramen is 
complete; in Orca the same; in Globiocephalus very nearly so; also in some of the 
true Delphini, as D, tursio, In Beluga, Platanista, and Phocena it is a mere groove. 
In the Cachalot the last-named condition is found, though the groove is relatively 
smaller and shallower than in other genera. It is bounded in front by the sharp, 
prominent upper edge of the condylar articular surface, behind by the lateral part of 
the neural arch; internally it descends into the neural canal at its upper and outer 
angle, and externally is gradually lost in the anterior surface of the upper part of the 
transverse process. 
The inferior edge of the bone presents a tolerably regular curve, the middle part 
descending 4 inches lower than the sides. When seen from below, it appears 
slightly hollowed in the middle in front, and posteriorly presents a broad obtuse 
triangular prominence, which fits into a corresponding depression in the axis, A 
similar process of the atlas occurs in all other Cetaceans in which this bone is separate ; 
but in the Cachalot it is shorter and more massive than in Beluga, Monodon, or 
