20 THE BRITISH MAMMALS : ORDERS, FAMILIES, ETC. 



In the Leporidae there are four upper incisors, at birth there are 

 six. The skull is laterally compressed ; the postorbital process is 

 large and wing-shaped ; the infraorbital opening is small. There 

 are three premolars in the upper jaw, two in the lower ; the molars 

 are without roots and have transverse folds of enamel. 'Jhe tibia 

 a-nd fibula are united. The hind legs are long; the tail is short. 

 The only British genus is Lepus (Plate XIV., 46 to 48). 



In the Ungulata the toes have hoofs or broad nails, the digits vary 

 in number from one to five, the scaphoid and lunar of the wrist are 

 distinct, the radius and ulna are in some cases united, there are 

 generally no clavicles. The molar teeth have broad crowns, and, as 

 a rule, distinct roots ; they may be " lophodont," that is, traversed 

 by ridges generally transverse to the long axis of the jaw, " buno- 

 dont," with tuberculated crowns, or " selenodont," with crescent- 

 shaped crowns, and "hypsodont," that is, with the crown long and 

 the root short, or "brachyodont," with the crown short and the root 

 long. There are ten sub-orders, of which only one, the Artiodactyla, 

 is represented in these islands. 



In the Artiodactyla the digits are even in number, the third and 

 fourth being equal in size or nearly so, and placed one on each side 

 of the median axis of the foot. The femur is without a third tro- 

 chanter. The dorso-lumbar vertebras are nineteen ia number, the 

 ribs are twelve, thirteen, or fourteen. The nasals are not expanded 

 behind. The premolars have one lobe, the molars have two. There 

 are fifteen families, with only two of which, the Bovidas and Cervidas, 

 we are here concerned. 



In the Bovidae only the third and fourth digits are functional, and 

 their confluent metapodials form the cannon bones ; the second and 

 fifth digits are incomplete and their metapodials rudimentary or 

 absent. In each jaw are three molars and three premolars in con- 

 tinuous series ; there are no upper incisors and frequently there is 

 no upper canine ; there are three pairs of lower incisors, close tc 

 which, and similar in character, is the lower canine. The horns are 

 permanent, and consist of a horny sheath on a bony core. The only 

 British genus is Bos (Plate xv., 49). 



The Cervidae differ from the Bovidas in the horns, when present, 

 being solid, without cores, deciduous, and generally branched. 

 Except in one genus (Cervulus) the first and second phalanges of the 

 second and fifth digits are present, frequently with traces of their 

 metapodials. There are two orifices to the tear duct, and the 

 lachrymal bone does not articulate with the nasal owing to the large 

 size of the vacuity. The first molar in both jaws is brachyodont ; 

 the upper canines are generally present and occasionally large. 

 There are two genera on our list, Capreolus and Cervus (Plates xvi., 

 xvii., and xviii., 50 to 52). 



The Cetacea are more or less fish-like in shape, and live in the 

 water, but in no other respect do they resemble fishes. The fore 

 limbs are modified into flippers; the hind limbs are reduced to 

 rudiments ; the tail is expanded into lateral flukes. The bones are 

 spongy, the cavities filled with oil. There are no clavicles, the 

 scapula, radius and ulna are flattened. There is no sacrum, the 



