APPENDIX 



overhangs the blowholes and is asymmetrical, the right side 

 being much more strongly developed than the left. 



The facial portion, or rostrum, of the right whales is 

 narrow and greatly arched, but in the Balaenopteras it is 

 wide and flat; in the toothed whales it may be either wide 

 and concave, as in the Physeteridae, or narrow and beak-like 

 as in the Ziphiidae and Delphinidae. 



The neck, or cervical, vertebrae of all the Cetacea are ex- 

 ceedingly thin and plate-like and usually either two or three 

 of the entire series are fused. In large-headed species, such 

 as the right whales, the neck is reduced to a minimum and 

 the cervical vertebrae are all joined in a solid mass to bear 

 the weight of the enormous skull. 



The remainder of the spinal column, as in all mammals, is 

 divided into dorsal, lumbar and caudal vertebrae. The first 

 series bear ribs and the last, which are those of the "tail 

 region," may be distinguished by the V-shaped "chevron 

 bones" attached to the lower side of each vertebral body; 

 because of the absence of functional hind limbs no sacrum 

 is present. 



The ribs of the whalebone whales differ from those of 

 other mammals because all but the first two or three have 

 lost the capitulum, or head, and articulate by only the tuber- 

 culum to the transverse processes of the vertebrae. 



In the baleen whales the sternum, or breast bone, is so 

 reduced that it only articulates with the first pair of ribs, 

 the lower ends of those remaining being free. Thus with 

 the weak attachment of the ribs to the vertebrae and no 

 fastening to the sternum, a loose "thoracic box" is formed, 

 which is capable of great lateral movement as the enormous 

 lungs expand and contract. 



In the toothed whales conditions are somewhat different. 

 Many of the ribs have the normal attachment by head and 

 tubercle to the vertebrae and are joined by their lower ends 

 to the sternum, which consists of several pieces; thus the 

 thoracic box is much more rigid than in the baleen whales. 



The bones of the fore-limbs of ordinary mammals are 



317 



