WHALES DOLPHINS. 379 



fibrous tissue. The result of this arrangement, which 

 will be better understood by a reference to the figure of 

 the skull of the Greenland Right- Whale at p. 386, is 

 that the cavity of the mouth is of extraordinary capacity, 

 and in the live animal it is entirely filled by the great 

 ranges of baleen-plates, which are covered when the 

 mouth is closed by the wide and deep lower lip. These 

 Whales feed principally on minute Mollusks and Crus- 

 taceans as well as on smaller Fishes, and this structure 

 of the mouth is admirably adapted for their capture. 

 "Opening its huge mouth," says Prof. Huxley, "and 

 allowing the sea-water with its multitudinous tenants to 

 fill the oral cavity, the Whale shuts the lower jaw upon 

 the baleen- plates, and straining out the water through 

 them, swallows the prey stranded upon its vast tongue." 



The Balaenoid Whales are further distinguished by the 

 presence of olfactory organs, though in a comparatively 

 undeveloped condition, by the double orifice of the blow- 

 hole, by the very slight manner in which the ribs are 

 articulated to the vertebrae, and by the form of the breast- 

 bone or sternum, which consists of only a single piece, 

 and is attached to the first pair of ribs only. The verte- 

 brae of the neck may either be united into a solid mass, 

 as in the Right- Whales, or may be all free, as is usually 

 the case in the Rorquals. Two well-marked families, 

 Balcenida and Balcenopteridte, are represented in our fauna. 



In the second sub-order, the Odontoceti, baleen is never 

 found, and there are originally always true teeth, though 

 they are sometimes lost early in life ; often they are very 

 numerous, and they are always single-rooted and similiar 

 to one another. The skull is usually very asymmetrical, 

 or laterally distorted; sometimes, as in Physeter and 

 Hyperoodon, it is wonderfully modified by the develop- 

 ment of raised ridges and crests on the maxillary bones. 



