272 THE SCIENCE OF LIFE. 



and habits. They are the largest of all living forms, 

 and, next to the Elephant, have the heaviest brains. 



FIG. 166. The Skeleton of Bat. cl. Clavicle, h. Humerus. cu. Ulna. c. Radius. 

 ca. Carpus. j>o. Thumb, -me. Metacarpus, ph. Phalanges, o. Scapula, f. Femur. 

 ti. Tibia. 



The nostrils are on the top of the head, and constitute 

 the blow holes, or spiracles. This order includes the 

 Whales and Dolphins. All have a large horizontally 

 flattened caudal fin. The head is large, often forming 

 half the bulk of the animal. The Whalebone Whales 

 (BalcsnidcB) are toothless, but in the Greenland Whale, 

 the largest of the group, which sometimes attains a 

 length of sixty or seventy feet, we find rudimentary 

 teeth in the embryo. The Toothed Whales (Odontoceti) 

 have many conical teeth in the lower jaw. The Sperm 

 Whales are in this division. In them the head is large 

 and abruptly truncated, and the nostrils are at the end 

 of the muzzle. The Delphinida, comprising the Dol- 

 phins, Narwhals, and Porpoises have teeth in both jaws. 

 Many Cetacea have very small organs of smell, and in 

 the Dolphins and Porpoises they are wanting. 



