BIRENIANS OR SEA-COWS. 595 



metres long, the female having no yicsible teeth ; there being 

 two rudimentary incisors which never appear through the 

 gum. It ranges from Hudson's Straits to the Arctic seas, 

 having formerly been seen along the coast of Labrador. To 

 the family of dolphins and porpoises belong the white whale 

 or DelpMnapterus leucas Pallas, which ranges from the Gulf 

 of St. Lawrence northward ; the grampus {Grampus griseus 

 Ouvier) ; the blackfish, of which there are two species, one 

 GloMcejjhalus melas Trail, ranging north of New York, and 

 one G. IracTiypterus Cope, to the southward, and the por- 

 poises, of which the most common on our coast is Pliocmna 

 irachycium Cope ; the rarer is P. lineata Cope. On the 

 coast of Labrador, as well as northward, occurs the thrasher 

 whale or killer {Orca gladiator Gniy) which has large 

 teeth, and a high dorsal fin ; it attacks whales, gouging out 

 the flesh from their sides. Certain fossil whales were pigmies 

 in size ; while the Zeuglodon of the Alabama Eocene Ter- 

 tiary beds, was an enormous serpent-like whale, which must 

 have measured over seventy feet in length. 



Order 6. Sirenia.— In the few species of sea-cows represent- 

 ing this order, the lower jaw is more as in other mammals, 

 having well developed ascending rami and normal transverse 

 condyles and coronoid processes. The teeth are well developed, 

 both incisors and molars, the latter with flattened or ridged 

 crowns, adapted for the trituration of vegetable food. A 

 neck is indicated ; the two nostrils are situated at the 

 upper part of the snout, and the lips are beset with stiff 

 bristles, while the mammae are pectoral. The fore limbs are 

 of moderate length, with five well-developed digits, but still 

 fin-like and bent at the elbow. The brain is narrow com- 

 pared with that of cetaceans, and the heart is deeply fissured 

 between the ventricles. The manatees of America and the 

 dugong of Australia and India (Fig. 518) live in the mouths of 

 large rivers, feeding on seaweeds, aquatic plants, or the grass 

 along the shore. The Florida manatee {Manatus Ameri- 

 canus Desmarest) grows to a length of from two to nearly 

 three metres. It ranges from Florida to the Amazons, where 

 it is called Vacca marina ; it ascends the river as far as Pebas, 

 Peru, and is killed and eaten, its flesh resembling beef. 



