652 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 57. 



characterizations of this group have not been well defined. Thus 

 vertebrate paleontologists have usually recognized only one living 

 genus of peccaries, ^^ Dicotyles" { = Tayassu), and to this group the 

 earlier writers referred most of the fossil forms discovered, although 

 it is now known that most, if not all, these species belong to extinct 

 genera. There has likewise been a decided tendency among paleon- 

 tologists to consider the peccary group as a whole as of only sub- 

 family rank, although some later writers have followed the mammalo- 

 gists in classifying the suillines under two distinct families, the 

 Suidae and Tayassuidae, but they have done this without giving 

 any particular reasons for this change of opinion; in fact there 

 seems to have been considerable reluctance on the part of paleontolo- 

 gists in following the mammalogists both in their recognition of two 

 distinct genera of living peccaries, and in admitting full family dis- 

 tictions between the peccaries and true pigs. A study of the litera- 

 ture suggests this attitude has been due, in part at least, to the 

 lack in definitions given for living forms of characters based on osteo- 

 logical features. And added to this the idea seems to prevail among 

 paleontologists that the known extinct forms, especially of the older 

 formations, rather definitely unite the two suilline groups in a single 

 family. 



In this connection it may be stated that Matthew and Gidley^ 

 several years ago pointed out that the known peccaries, both living 

 and extinct, are confined in their distribution entirely to the New 

 World, while the true pigs seem as exclusively to belong to the Old 

 World, and they expressed the opinon at that time that these two 

 groups comprise subfamilies derived from "the primitive Suidae, 

 common to both hemispheres in the Oligocene." Matthew later ^ 

 somewhat modified this arrangement in giving full-family rank 

 to the pig and peccary groups, and suggested their derivation, 

 together with the Elotheriidae, " from a common Eocene ancestry." 

 My present view fully accords with this later conclusion except 

 that, from certain modifications observed in the earliest known 

 forms, I believe the elotheres must have split off from the primitive 

 ancestral group at a very much earlier date than that which marked 

 the definite separation of the Suidae and Tayassuidae. 



From the foregoing it seems evident that the definitions of the 

 two families of suillines, and especially the two genera of living 

 peccaries (one of which is not even now recognized by paleontolo- 

 gists), are in this connection in need of revision since these defini- 

 tions have a special bearing on any attempt to clear up and make 

 determinable the Pleistocene species of peccaries. I therefore deem 

 them necessary to an intelligent description of any new material. 



> Bull. Amer. Mus. Nat. Hist, vol. 20, 1904, p. 267. 

 'Idem., vol. 23, 1907, p. 2] 6. 



