Many of these extinct Lemuroids so combine the characters of the _Insectivora_ and the _Ungulata_ (or hoofed animals), with those of their own Sub-order, that it is often extremely difficult, even impossible, sometimes, to determine to which Order they really belong, owing to a blending of characters due to their common origin. The Upper Eocene forms present many affinities with the South American Capuchin Monkeys (_Cebidæ_). Dr. Forsyth Major is of opinion, however, that they are more highly, and not (as is generally believed) less specialised than those now living, which appear to have been the subject of retrogressive development. The species to be noticed below are some of the more important of those which have been ascertained to belong to the present Sub-order. No remains assignable with certainty to the families _Chiromyidæ_ or _Tarsiidæ_, have as yet been discovered. The first form {112}to be mentioned belongs to a family which has now no living representatives. FAMILY MEGALADAPIDÆ. This family has recently been established by Dr. Forsyth Major, for a fossil species represented by the greater portion of a large cranium and part of its lower jaw, found in a marsh at Amboulisatra, on the south-west coast of Madagascar. This species is the only representative of the single genus of the family. GENUS MEGALADAPIS. _Megaladapis_, Forsyth Major, Phil. Trans., vol. 185 B, p. 15 (1894). The cranium, about 10 inches long, indicates an aged animal three or four times as long as the common Cat, which is an enormous size as compared with any living Lemur. Brain-case straight, narrow, short, low, and situated at a higher level than the facial region; an enormous lateral development of the region between the eyes; orbits small in diameter, communicating freely with the temporal fossa, protruding outwards and forwards, and surrounded by a thickened ring; facial region elongate and bent upward; palate convex downwards from front to back; ridges for attachment of the temporal muscles uniting in a great central crest; frontal bones constricted behind the orbits; maxillary bones behind the molar teeth greatly inflated by air-cavities; the two halves of the lower jaw ossified together. In the upper jaw the pre-molars have one outer and one inner cusp, and the molars one internal and two external cusps, the former being deeply separated from the hind outer cusp, and joined by a ridge to the front outer cusp. In the lower {113}jaw, the posterior pre-molar has one outer cusp, a fore and hind inner cusp (each joined by a crescent to the outer cusp), and a central inner cusp; the three molars have two outer and three alternating inner cusps, and to the outer side a basal cingulum; the posterior molar has a strongly cusped heel.