Altogether some sixty species of Deer are known, of which the preponderance are Old-World forms. The Deer of the Old World are distributed among the genera[199] _Cervus_ (all Europe and Asia); _Cervulus_, the Muntjacs (India, Burmah, China, etc.); _Hydropotes_ (Eastern China); _Capreolus_ (Europe and Central Asia); _Elaphodus_ (Eastern China); there is one American _Cervus_, the Wapiti. The American genera are _Cariacus_ and _Pudua_. The Elk (_Alces_) and the Reindeer (_Rangifer_) are circumpolar. The principal structural modification which occurs within {293} the family Cervidae concerns the rudimentary fifth and second toes. In _Capreolus_, _Hydropotes_, _Moschus_, _Alces_, _Rangifer_, and _Pudua_ there are considerable remains of the lower parts of metacarpals II. and V.; in the other genera smaller traces of the upper ends of the same bones. The two most abnormal genera are _Moschus_ and _Hydropotes_, more particularly the former, which neither Sir V. Brooke nor Professor Garrod allow to be members of the family at all. _Moschus_ is usually placed in a special sub-family by itself, Moschinae, the remaining Deer being referred to another sub-family, Cervinae. SUB-FAM. 1. CERVINAE.--The genus _Cervus_ comprises rather over twenty existing species, which, except the Wapiti (_C. canadensis_), are exclusively Old World in distribution. The principal features of variation in the genus, in accordance with which it has been divided up into sub-genera, are (1) palmated (Fallow Deer, _Dama_) or non-palmated antlers; (2) adults spotted with white at all ages and seasons (_Axis_), or in summer only (_Pseudaxis_), or not at all; (3) spotted or unspotted young; (4) existence or absence of rudimentary canines in the upper jaw. Among the members of this genus, _Cervus (Elaphurus) davidianus_ is interesting as having been first observed by the missionary Pere David in a park belonging to the Emperor of China near Pekin. Its horns are remarkable for dividing early into two branches of equal length, of which the anterior again branches into two. Specimens of this Deer were ultimately obtained for the Zoological Society's Gardens.