616 CARNIVORA. 



and lunar are fused in the carpus, and there is no centrale. 

 The femur is without a third trochanter. The pollex and 

 hallux are not opposable, and the digits are nearly always 

 provided with sharp claws. The bears are plantigrade ; the 

 others either digitigrade or semidigitigrade (sub-plantigrade). 



In some forms, particularly the Felidae, the claws are 

 retractile. The retraction consists in the folding back of the 

 ungual phalanx into an integumentary sheath, placed in the 

 manus on. the outer or ulnar side of the middle phalanx of the 

 digit, in the pes on the dorsal surface* of the corresponding 

 phalanx ; it is effected by an elastic ligament connecting the 

 two phalanges. The straightening out of the phalanges and 

 consequent protrusion of the claws is caused by the contrac- 

 tion of the flexor profundus digitorum muscle. 



The cerebrum is fairly large and usually well convoluted, 

 but it never completely covers the cerebellum. 



The stomach is simple and the large intestine is generally 

 provided with a caecum (absent in Ursidae) which is however 

 short. 



The testes descend into a scrotum, and there is generally 

 an os penis. The glans penis, which is frequently covered 

 with recurved hooks, swells in some forms (e.g. Canidae) 

 during the act of copulation so that it cannot be withdrawn. 

 Vesiculae seminales are always absent, and Cowper's glands 

 are present or absent. 



The ovaries are contained in peritoneal sacs ,and the 

 uterus is bicornuate. The mammae are abdominal or thoracic 

 and the placenta is always zonary. 



The living Carnivora may be classified in three sections, 

 the cat-like or Aeluroidea, the dog-like or Cynoidea and the 

 bear-like or Arctoidea. The characters utilised are taken 

 from certain features of the base of the skull around the 

 tympanic region and agree fairly well with the characters 

 afforded by the dentition and other parts of the body. 



The Aeluroidea including the Felidae, Viverridae, Hyaenidae 

 and Protelidae present the following features. The auditory 

 bulla is dilated and nearly divided into two chambers by a 

 septum ; the lower lip of the bony auditory meatus is very 

 short ; the paroccipital process is closely applied to the 

 * And to a certain extent on the fibular side. 



