XIII 



PHYLUM CHORDATA 481 



apertures on its upper surface. The cervical vertebrae (of which 

 there are only six in the Manatee) are not fused. A clavicle is 

 absent. There is a distinct, though small, articulation between the 

 humerus and the bones of the forearm. There are never more 

 than three phalanges in any of the digits. The pelvis is represented 

 by a pair of vertically situated vestiges. The anterior part of the 

 palate and the symphysis of the mandible (which is prolonged) are 

 covered with rugose, horny plates. The epiglottis and arytenoids 

 are not prolonged as they are in the Cetacea. The brain is com- 

 paratively small, and the convolutions are not highly developed. 

 The testes are abdominal. The teats are two in number and 

 pectoral in position. The uterus is two-horned. The placenta is 

 noD-deciduate and zonary. 



This order includes among recent forms only the living Dugong 

 (ffalicore) and Manatee (Manatus), and the recently extinct 

 Rhytina. 



ORDER 4. UNGULATA. 



Terrestrial, chiefly herbivorus, Eutheria, with the fur abundant 

 or scanty, with the terminal phalanges, on which the weight of 

 the body usually rests, nearly always invested in solid horny hoofs. 

 The teeth are heterodont and diphyodont; the canines usually 

 absent or small, and the premolars and molars well developed, 

 with broad crowns having tuberculated or ridged surfaces. The 

 clavicle is absent; the humerus has no foramen over the inner 

 condyle : the scaphoid and lunar of the carpus are always 

 distinct. The villi of the placenta are diffuse or gathered into 

 patches the cotyledons. 



SECTION 1. UNGULATA VERA. 



Ungulata in which the feet are always unguligrade, with never 

 more than four functional digits. The os magnum of the carpus 

 articulates with the scaphoid. The testes are contained in a 

 scrotum. The teats are usually four, and situated far back, 

 never exclusively thoracic in position. The uterus is two-horned, 

 The allantois is large, the placenta non-deciduate, and the villi 

 diffuse or gathered into cotyledons. 



This section comprises all the typical Ungulates. 



Sub-order a. Perissodactyla. 



Ungulata vera in which the third toe of both manus and pes 

 is larger than the others and symmetrical in itself, and in which 

 there is a tendency to reduction of the others. The femur has a 

 third trochanter. The tibial articular surface of the astragalus 

 is pulley-shaped ; the distal surface flat and more extensively 

 related with the navicular than with the cuboid ; the calcaneum 



