The femur has the head much higher than the greater trochanter, which is a feature common to elephants, _Diprotodon_, _Arsinotherium_, etc., so that it must be looked upon as an adaptation. The third trochanter has disappeared, and in elephants, it is lost in the advanced forms, remaining however as a trace in _Palaeomastodon_. The tibia is very short and massive and hardly gives any suggestions of relationship, except that it is not fused with the fibula at the upper end, in which it is in strong contrast to the toxodonts. While in the table of comparisons numbers 1, 2, 3, 4, 8, 9, 10, 14, 17, 19, 20, and 21 may be, in part, or wholly, interpreted as adaptations, and alone would not be at all conclusive of relationship to elephants, numbers 1, 5, 6, 7, 8, 11, 12, 13, 15, 18, and 21 point toward the elephants as the close relatives of the _Pyrotheria_. In the first series of points there are none which mitigate against associating these two groups, while if the attempt is made to associate _Pyrotherium_ with any group other than _Proboscidea_ there are strong points, and a number of them, which would prevent this association. As a result of the foregoing, together with a feeling which continued handling of the specimens has given me, I can come to no other conclusion than that the _Pyrotheria_ should be placed under _Proboscidea_. In his Linea Filogenetica de los Proboscideos, Ameghino assigns to this suborder, or at least puts into the phylogenetic tree, a considerable number of forms from the Casamayor beds, all of them genera with bunodont molars, usually known by but one or two teeth, such as _Asmithwoodwardi_, _Nephracodus_, _Cephanodus_, _Paulogervaisia_, and the better known genera, _Carloameghinia_, and _Didolodus_, all of which he makes ancestral to _Pyrotherium_. So far as known, however, these forms show none of the peculiarities of the _Pyrotherium_ skull or dentition, so that it is difficult for me to see any reason for including them even in the suborder. The genus _Carlozittelia_, from the upper Casamayor, is in a different position, having an enlarged upper incisor (found isolated) and molars of the bilophodont type. I should include this in the family Pyrotheridae and none of the others. =Pyrotheriidae= Ameghino All the forms assigned to this family are supposed to be closely related to _Pyrotherium_ and to have much the same structure. Ameghino has proposed the following genera, _Pyrotherium_, _Parapyrotherium_, _Richardowenia_, _Archaeolophus_, _Propyrotherium_.