FAM. 8. ANTILOCAPRIDAE.--This family contains but one genus and species, the N. American "Pronghorn," _Antilocapra americana_. This animal deserves a family to itself on account of the singular structure of the horns, which are intermediate in character {307} between those of the Deer and those of the Antelopes. They are unquestionably "hollow-horned" Ruminants, in that there is an osseous horn core, upon which lies the actual horn. This, however, is softer than in Bovidae, and is semicorneous. It is, indeed, more like the velvet of the stag's horn. Moreover the horn is branched, and there are sometimes even three prongs. Furthermore, it is now certainly known that the Pronghorn sheds its horns not merely occasionally, but with definite annual periodicity. It so far resembles the Deer. But it must be borne in mind that in the Deer the horn shedding is a twofold process. There is first of all the stripping off of the velvet, and secondly the shedding of a portion of the horn core down to the burr. What happens in the Prongbuck is the shedding of the true horn only ( = the shedding of the velvet), _not_ of the horn core. It appears, however, that occasionally (once in their lifetime?) certain undoubted Antelopes may cast their horns.[209] Another external character of this animal is the total absence of "false hoofs," the last vestiges of the second and fifth digits. The Pronghorn is a gregarious creature running in bands of six up to hundreds. FAM. 9. BOVIDAE.--This family, more extensive than that of the Cervidae, contains not only the Oxen, Sheep, and Goats, but also the Antelopes, save only _Antilocapra_, which must be placed in a family by itself. The only two points which distinguish all Bovidae from all Cervidae[210] are the nature of the horns already described, and the polycotyledonary condition of the placenta. Moreover the horns are usually present in both sexes, though there are exceptions, such as the Sheep and Goats, and various genera of Antelopes (_Tragelaphus_, _Tetraceros_, etc.). There are never the first two phalanges belonging to the rudimentary digits II., V., as there are in all Deer excepting _Cervulus_. There is as a rule but one orifice to the lachrymal duct. There are never persistent upper canine teeth in either sex.