ARTIODACTYLA. 757 



tarsals are fused in Tragulus^ free in the other genus Dor- 

 catherium ; the fibula is complete. There are no upper incisors, 

 the upper canines are long and pointed, especially in the males ; 

 the lower canines are like incisors ; the dental formula is 



~^. The Chevrotains ruminate, and the stomach is divided 



into three chambers, the many-plies being rudimentary. The 

 placenta is diffuse. The Chevrotains are often confusedly 

 associated with the musk-deer (Moschus), with which they have 

 no special affinities. 



Species of Tragulus (smallest among living Ungulates) occur in 



Indo- Malaya, India, and Ceylon ; one species of Dorcatherium, 



of aquatic pig-like habits, is found on the west coast of Africa. 



Group 4. Pecora or Cotylophora the true ruminants, including 



deer, giraffes, cattle, and sheep. Only the third and fourth 



FIG. 407. Stomach of sheep. From Leunis. 



a, QEsophagus ; c, rumen or paunch ; </, reticulum or honeycomb- 

 bag ; tf, psalterium or many-plies ; f, abomasum or reed ; , 

 beginning of duodenum. 



digits are complete, the fused third and fourth metacarpals and 

 metatarsals form "cannon bones." In the embryos of ox and 

 sheep, the second and fifth metacarpals and metatarsals are also 

 represented ; the second metacarpal and fifth metatarsal are 

 unstable and soon disappear ; small traces of the fifth metacarpal 

 and second metatarsal persist. The fibula is represented by a 

 small nodular bone articulating with the lower end of the tibia, 

 and forming the external malleolus. There may be in addition 

 a rudiment of the proximal end attached to the upper part of 

 the tibia, but the two parts are never united. Paired outgrowths 

 of the frontal bones are common, capped with horny sheaths in 

 the Bovidse, deciduous and restricted to the males in almost 

 all Cervidae. There are no upper incisors, and rarely upper 

 canines ; there are three pairs of lower incisors, which bite 

 against the hardened gum above ; and the lower canine resembles 

 and is in the same series as the incisors ; the typical dentition is 



^3J. The stomach has four distinct compartments. The placenta 



