438 



METAZOAN PHYLA 



Fig. 334. — Three-toed sloth, Bradypus tridactylus. A member of the hairy edentates, 

 found in the forests of tropical America, it is entirely arboreal and adapted to hanging, back 

 downward, from branches of trees by its long, curved claws, and as an adjustment to this 

 habit it can rotate its head 180 degrees. In the damp forests sloths commonly have green 

 algae growing on their hair. This condition, together with their exceedingly slow move- 

 ments, renders them inconspicuous among the foliage. The hair on the legs and underside 

 of the body forms a water-shedding device by being directed downward. Sloths have 

 short jaws with teeth, the tail is short or absent. The three-toed sloth has nine cervical 

 vertebrae, whereas the two-toed form has but six. (Photographed from a specimen in the 

 University of Nebraska State Museum.) 



Psa/fer/'um 



Esophagus 



Abofnersum 



Rumer? 



Fig. 335. — A ruminant stomach. The arrows show the direction of movement of the 

 food. The balls of cud pass down the esophagus and into the rumen; then into the reticu- 

 lum and back to the mouth; on the second swallowing the food enters a small passage in 

 the upper part of the reticulum formed by the apposition of folds, or valves, and is directed 

 into the psalterium. From several sources. 



