CARNIVORA. 717 



the insertion of muscles of neck and jaw. The glenoid 

 fossa for the articulation of the lower jaw is deeply concave, 

 and bounded by a large postglenoid process, the result 

 being that the lower jaw can only move up and down. 

 This is important, as it minimises the risk of any failure 

 of grip in seizing living prey. The muscles of the lower 

 jaw are very strongly developed, and with this may be 

 associated the strength and the protrusion of the zygomatic 

 arch in the more specialised types. The widening of this 

 arch has prevented the formation of a frontal bridge behind 

 the orbit, so that the orbit is confluent with the temporal 

 fossa. There is a strongly developed and ossified tentorium 

 descending between cerebrum and cerebellum. The 

 tympanic bullae are in most cases large. 



The clavicles are incomplete or absent (an important 

 contrast with all Insectivora except Potamogale) ; the radius 

 and ulna are always distinct ; the fibula is slender but 

 distinct. 



The cerebrum is well convoluted, and the cerebellum is 

 more or less covered by the cerebrum. 



The stomach is always simple ; the caecum is absent, or 

 short, or simple ; the colon is not sacculated. 



There are no vesiculae seminales. The uterus is bicor- 

 nuate. The mammae are abdominal. The placenta is 

 deciduate and zonary. 



Representatives of Carnivora are found in all parts of the 

 world. 



Sub-Order Carnivora Vera or Fissipedia. 



The true Carnivores are for the most part terrestrial. The incisors 

 are almost always -, the canines are usually large ; one of the 



back teeth is modified as a trenchant carnassial or sectorial. 



The digits generally have sharp claws, which may be retractile. 



Within the sub-order there are three sections' — /Eluroidea, 



Cynoidea, and Arctoidea — represented respectively by cat, 



dog, and bear, but these types are connected by extinct 



forms. 



In retractile claws, the last phalanx of the digit with its attached 



claw is drawn back into a sheath on the outer side of the middle 



phalanx in the fore-foot, on the upper side in the hind-foot. When 



the animal is at rest or is walking, the claw is retained in this bent 



position by an elastic ligament, and is in this way protected from 



wear. When the animal straightens the phalanges, the claws are 



protruded. 



