SIRENIANS OR SHA-COWS. 595 
metres long, the female having no visible 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 Delphinapterus leucas Pallas, which ranges from the Gulf 
of St. Lawrence northward ; the grampus (Grampus griseus 
Cuvier) ; the blackfish, of which there are two species, one 
Globicephalus melas Trail, ranging north of New York, and 
one @. brachypterus Cope, to the southward, and the por- 
poises, of which the most common on our coast is Phocena 
brachycium Cope; the rarer is P. lineata Cope. On the 
coast of Labrador, as well as northward, occurs the thrasher 
whale or killer (Orca gladiator Gray) 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 mamme 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 Amert- 
canus Desmarest) grows to a length of from two to nearly 
three metres: It ranges from Florida to the Amazons, where 
itis called Vacca marina ; itascends the river as far as Pebas, 
Peru, and is killed and eaten, its flesh resembling beef. 
