38 MARINE AND AQUATIC TEE8PASSERS. 



of notice. In the Spermaceti Whale the teeth are 

 almost entirely confined to the lower jaw, whereas, in 

 the Greenland Whale, the substitute for teeth is en- 

 tirely confined to the upper jaw. Each structure 

 answers the same purpose, but is altered to suit the 

 material on which it has to work. 



From the upper jaw start some six hundred plates 

 of whalebone, or " baleen/' as it is more properly 

 called. In one species, the Rorqual, there are no less 

 than five thousand of these plates. They vary in size 

 according to the size of the individual, and the position 

 which they occupy in the mouth ; but in a full-grown 

 whale, the largest plates will measure some thirteen 

 feet in length, and nearly a foot wide at the base. 

 They become rather narrower towards the point, but 

 are there split up into fan-like sprays of hair-like 

 fibres. The plates of baleen vary much in length, 

 those at the tip of the jaw being the longest, and those 

 at the base the shortest, so that when the mouth is 

 partly opened, the baleen forms a sort of cage all 

 round it. 



The mode in which these plates enclose the opened 

 mouth may be seen from the accompanying illustra- 

 tion. Some years ago, when I was living in Paris, I 

 was greatly struck with the fine skeleton of the Green- 

 land Whale that is kept in the Museum of Comparative 

 Anatomy in the Jar din des Plantes. In this admirable 

 specimen, the baleen has been retained in its natural 

 position, and as the mouth has been shown as it ap- 

 pears when open, the beautiful arrangement of the 

 plates is far better seen than would have been the case 

 with the jaws closed. 



