CETACEA. 577 



Fam. 2. Catodontida. The family of the CatodontidcB or 

 PhysteridcE comprises the Sperm Whales or Cachalots, with 

 which we commence the series of the Toothed Whales (Odon- 

 toceti}. They are characterised by the fact that the palate is 

 destitute of baleen plates, and the lower jaw possesses a series 

 (about fifty-four) of pointed conical teeth, separated by inter- 

 vals, and sunk in a common alveolar groove, which is only 

 imperfectly divided by septa. The upper jaw is also in reality 

 furnished with teeth, but, with a single partial exception, these 

 do not cut the gum. 



The best-known species of this family is the great Cachalot 

 or Spermaceti Whale (Physder macrocephalus, fig. 246). This 

 animal is of enormous size/averaging from fifty to seventy feet in 

 length, but the females are a good deal smaller than the males. 

 The 4iead is disproportionately large, as in the Jlalcenidce, 

 forming nearly one-third of the entire length of the body. 

 The snout forms a broad truncated muzzle, and the nostrils 

 are placed near the front margin of this. The Sperm Whales 



Fig. 246. Spermaceti Whale (Physeter macrocephalus). 



live together in troops or " schools," and they are found in 

 various seas, especially in the North Pacific. They are largely 

 sought after, chiefly for the substance known as " spermaceti ; " 

 but besides this they yield oil and the singular body called 

 " ambergris." The spermaceti is a fatty substance, which has 

 the power of concreting when exposed to the air, being in life 

 a clear white oily liquid. It is not only diffused through the 

 entire blubber, but is also contained in special cavities of the 

 head. The sperm-oil yielded by the blubber is exceedingly 

 pure, and is free from the unpleasant odour of ordinary whale- 

 oil. The ambergris is a peculiar substance which is found in 

 masses in the intestine, and is probably of the nature of a 

 biliary calculus, since it is said to be composed of a substance 

 very nearly allied to cholesterine. It is used both as a per- 

 fume itself, and to mix with other perfumes. 



Fam. 3. Delphinidcz. This family includes the Dolphins, Por- 

 poises, and Narwhal, and is characterised by usually possessing 



2 O 



