330 JIR. W. H. FLOWEE ON THE OSTEOLOGr 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 2^". 



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, arismg 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 chxular 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 JDelpJdni, as B. tursio. In Beluga, Platanista, and Phoccena it is a mei-e 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 



