574 MAMMALS. 



7. Orycteropidse — the Ethiopian Aard-varks, represented by two 

 species of Orycteropus, ranging from S. Africa to Egypt. They 

 are shy, nocturnal animals, living in burrows, feeding on ter- 

 mites. There are numerous complex teeth of two sets. The 

 skin bears scanty bristles. The mouth is tubular, and the 

 tongue is narrow and protrusible. The digits bear nails 

 suited for digging. The uterus is bicomuate, the placenta 

 broadly zonary. 



Order 2. Sirenia — Sea Cows. 



A small moribund order of sluggish, aquatic, seaweed- 

 eating Mammals, in no direct way connected with Cetaceans, 

 possibly related to Ungulates, but certainly primitive. 

 There are two living genera, Halicore (Dugong). and Mana- 

 tus (Manatee), and one recently exterminated (Jihytina.) 



The Sirenia are sluggish animals, with massive heavy 

 bones, a plump body, some oil, and sparse hair. They 

 are aquatic, with fish-like form, no trace of hind-limbs, 

 flipper-like fore-limbs, no external ear, valved nostrils, 

 networks in the arteries (useful in prolonged immersion). 

 They are herbivorous, and like others of similar habit 

 have a chambered stomach, a long intestine, and a csecum. 



They are primitive, and with this fact may be associated 

 the abdominal testes, the absence of separate epiphyses on 

 the vertebrae (as in Prototheria), the small, rather smooth 

 brain. 



The body is fish-like, the head rounded, the skin is 

 thick and tough, with sparse bristles, mostly about the 

 mouth. 



The paddle-shaped fore-limbs have, at most, rudimentary 

 nails ; there are no hind-limbs. The skull is not like that, 

 of Cetaceans. The nasals are, at most, rudimentary. There 

 are no canine teeth. The vertebrae have no epiphyses. 

 There are chevron bones below the tail. There are no 

 clavicles. The pelvis is rudimentary. 



The brain is small and has few convolutions. The nostrils 

 are valved, and lie at the end of the snout. The small 

 eyes have imperfect eyelids, but have a nictitating mem- 

 brane. There are no external ears. In the mouth there 

 are horny crushing plates. The stomach is chambered, 

 and there is a caecum. The ventricles are separated by a 



