FAMILIES OF ARTIODACTYLA. 579 



psalterium is a. filter, its lining membrane being raised into numerous 

 leaf-like folds covered with papillae. Along these the food passes to 

 the reed, which is the truly digestive stomach, for its smooth walls 

 secrete the gastric juice. 



Cervidse — the widely distributed deer, absent only from the 

 Ethiopian and Australian regions. The second and fifth digits 

 are usually represented, often along with the distal parts of the 

 corresponding metacarpals and metatarsals. The upper canines 

 are usually present in both sexes. The horns, if present, are 

 antlers, confined to the males and deciduous, except in the rein- 

 deer where they are possessed by both sexes and are permanent. 

 They are outgrowths of the frontal bones, are covered during 

 growth by vascular skin — the velvet, and attain each year to a 

 certain limit of growth. After the breeding season the blood 

 supply ceases, the velvet dies off, and an annular absorption 

 occurs near the base. Then the antlers are shed, leaving a stump 

 from which a fresh but larger growth takes place in the next year. 

 The earliest (Lower Miocene) deer had no antlers, thus resembling 

 young stags of the first year ; the Middle Miocene deer had 

 simple antlers with not more than two branches, thus resembling 

 two-year-old stags ; the parallel between the history of the race 

 and the individual development is, as regards antlers, very exact. 

 Examples : — Cervus, most Old World deer ; Rangifer, the rein- 

 deer ; Alces, the elk or moose ; Capreolus, the roe-deer ; Hydro- 

 fotes, the water-deer, without antlers ; Moschus, the musk-deer, 

 without antlers, with long sharp upper canines in the males, 

 with large musk-glands. 

 Giraffidse, represented solely by the giraffe ( Giraffa camelopardalis), a 

 tall Ethiopian animal, notable for its enormously elongated cer- 

 vical vertebrae, and for its long limbs. It is gregarious in its 

 habits, and feeds on the leaves of trees. The lateral digits are 

 entirely absent. The dental formula is -Uff. On both sexes 

 there are on the forehead short erect prominences, over the 

 union of parietals and frontals, which arise from the distinct 

 centres of ossification, but afterwards fuse with the skull. In 

 front of these there is median protuberance. 

 Antilocapridae, represented solely by the prongbuck {Antilocapra . 

 americana), a North American animal with most of the charac- 

 teristics of Bovidae, but with deciduous and branched horns. 

 Bovidae, the hollow-horned Ruminants widely distributed throughout 

 the world, but without indigenous representatives in Australia, 

 South or Central America. The second and fifth digits may be 

 completely absent, but are often represented by minute hoofs and 

 supporting nodules of bone. The frontal appendages, if present, 

 consist of a solid bony core growing from the frontal and a much 

 longer sheath of horn which grows at the base as it is worn 

 away at the tip. They are not deciduous and are usually present 

 in both sexes, though larger in the males. 

 Examples : — Antilope, Gazella, Capra, Ovis, Bos. 



