196 UNGULATA order vii 



early deciduous, or entirely wanting ; inferior canine incisiform. Diastema wide. 

 Cheek teeth selenodont, low, with several roots. Superior premolars short, with 

 ectoloph and well-developed internal crescent. Carpals {magnum and trapezoid) and 

 tarsals {cuboid and naviculare) partially co-ossified. Principal metap>odials {III. and 

 IV.) always fused to form a cannon hone. Lateral metapodials generally much 

 attenuated, either reduced or entirely suppressed, being preserved sometimes as 

 proximal, sometimes as distal rudiments with short phalanges. 



As in the Tragulidae, the entire skeleton of the Cervicornia is characterised 

 by a brittle bony substance with abundant osteoblasts, and by the thin nature 

 of the bones of the skull. 



The skull has an elongated subcylindrical form. The cranial and facial 

 axes are nearly in the same line and do not show the strong bending seen in 

 most Cavicornia. The arched brain-case is principally formed by the 

 parietal bones, yet the frontals enter into the formation of its narrower 

 portion ; laterally the squamosal bones acquire considerable extent. The 

 lachrymal bones are unusually large, and on their facial surfaces have de- 

 pressions, the so-called lachrymal fossae. Between the lachrymal, nasal, 

 frontal and maxillary bones, there is very frequently an ethmoidal vacuity 

 in the ossification leading into a space filled with thin lamellae of bone 

 and air cavities. The orbits are directed forward and completely surrounded 

 by bone. The most striking feature in the skull of many male deer 

 is the presence of antlers. This character, however, is merely incidental 

 in systematic value, for not only are these osseous structures absent in all 

 females except the reindeer, but in the oldest fossil forms are likewise wanting 

 in both sexes. The presence of antlers also exercises less influence on the 

 general structure of the skull than the horn cores of the Cavicornia. More- 

 over, similar antlered forms are of constant recurrence in various groups 

 of deer not closely related to each other. In the giraffes, Protoceratinae, etc., 

 the bony processes on the frontal bones are permanently covered with 

 integument. Usually, however, this skin is gradually worn off by rubbing, 

 leaving the antlers bare. After the rutting season the true antlers are 

 generally shed, thus exposing the basal osseous processes on which they are 

 borne. These are called pedicles. The nodose band at the base of the 

 antlers is known as the burr. In the forms with complex antlers, these 

 begin with a single prong or tine, which in the second year becomes a 

 bifurcated antler ; in succeeding years, one new tine is added to those already 

 present. The phylogenetic development also proceeds in a similar manner. 

 Antlers are entirely absent in the oldest Miocene forms. In the Middle 

 and Upper Miocene species of Palaeomeryx, they merely consist of a beam with 

 one or two tines ; similar also in Dicrocerus, but it is shed and renewed. In 

 the Pliocene, the deer start out with a short beam, a longer tine, and from 

 two to three accessory tines. But not until the Upper Pliocene, the 

 Pleistocene and Recent time have antlers displayed that luxuriance, size and 

 abundant branching observed in the stag, reindeer and elk, and most 

 conspicuously in the extinct Irish deer. 



In the Cervicornia the dentition (Fig. 271) lacks the superior incisors. 

 In the youngest representatives of the deer, the superior canines are also 

 either entirely wanting or appear only in the male and frequently are 

 shed early. The inferior canine has assumed the form and function of an 



