The whole order may be divided into the Ungulata Vera, containing the suborders Perissodactyla and Artiodactyla, and a somewhat heterogeneous assemblage of animals which may be called Subungulata or Ungulata Polydactyla. Cope has pointed out a character in the structure of the carpus by which the latter are differentiated from the former. Thus in all the Subungulata the bones of the proximal and distal row retain the primitive or more typical relation to each other (see Fig. 98); the os magnum of the second row articulating mainly with the lunar of the first, or with the cuneiform, but not with the scaphoid. But in the group to which the vast majority of modern Ungulates belong the second or distal row has been shifted altogether towards the inner side of the limb (see Fig. 99), so that the magnum is brought considerably into relation with the scaphoid, and is entirely removed from the cuneiform, as in the great majority of existing mammals. It will be on the whole more convenient to commence our survey of the members of this suborder with the more specialised group of the Ungulata Vera, in which the Artiodactyla will be taken first. UNGULATA VERA.[174] In the typical Ungulata the feet are never plantigrade, and the functional toes do not exceed four—the inner digit being suppressed, at all events in all forms which have existed since the Upper Eocene period.[175] The os magnum of the carpus articulates freely with the scaphoid. The allantois is largely developed, and the placenta, so far as is known, is non-deciduate; the chorionic villi being either evenly diffused or collected in groups or cotyledons (in Pecora). The testes descend into a scrotum. There is never an os penis. The uterus is bicornuate. The mammæ are usually few and inguinal, or may be numerous and abdominal (as in Suina), but are never solely pectoral. The cerebral hemispheres in existing Ungulates are well convoluted. The group is now, and has been throughout almost the whole of the Tertiary period, composed of two perfectly distinct sections, differing from each other, not only in the obvious characters of the structure of the limbs, but in so many other parts of their organisation that they must be considered as of the rank at least of suborders. The characters of these divisions, first indicated by Cuvier, were thoroughly established by Owen, by whom the names whereby they are now generally known were proposed. _Suborder_ ARTIODACTYLA.