The first molar (m ) presents four low thick cones, two internal and two external : each external cone is connected with its opposite internal one by a low ridge, swelling into a tubercle at the middle of its oblique course. The cingulum (cc) seems to be continued uninterruptedly round the crown of this tooth, thickest at the fore and back part, and at the interspace of the inner lobes ; and developing the small acces sory antero-external tubercle. The second molar (m 2) is similar to, but rather larger than, the first ; the tubercle on the oblique ridge connecting the two front lobes is less developed. The cingulum is obliterated on the inner side of the posterior lobe.
The last molar is rather narrower behind than m 2 ; the tubercle on the anterior of the oblique connecting ridges is smaller : that on the posterior ridge is almost obsolete.
In the last lower premolar (fig. 96, p 4 ) the division and development of the anterior lobe gives rise to a pair of cones, one external (a), the other internal (b) , connected anteriorly by a basal ridge, in front of which is the fore part of the cingulum. The low posterior lobe (c) shows the rudiment of a second internal cone (d).
The first molar (fig. 96, mi) has a pair of front lobes and a pair of hind lobes, with an oblique ridge continued from postero-internal lobe to the interspace between the front pair.
The second molar (n, 2) shows an increase of size ; but its chief and most interesting modification is the development of a tubercle (e) between the two anterior lobes, making three cones on the same transverse line, and thus repeating the character of the molar tooth of Stereognathus (fig. 97, e). The oblique ridge from the outer
and hinder lobe (c) abuts against the inter mediate tubercle (e). The nearest approach to the above dentition is made by the extinct Hyratotherium ; also a fossil from the London clay.
The third trochanter on the femur of Pliolophus, and the association of three metatarsals in one portion of the matrix, as if belonging to the same hind foot, confirm the essentially perissodactyle affinities of that genus as shown by the skull and teeth. Pliolophus and Hyracotlierium form a well-marked section in the lophiodont family, which seems to have pre ceded the palmotherian family in the order of appearance, and to have retained more of the general ungulate type than that family. This is shown by the graduation of the tapiroid modification of the molar teeth into one more nearly resem bling that of the Anthracotheria and Chceropotami, by the absence of the postero-internal cone on the ultimate premolar, by which all the premolars are, as in artiodactyles, less com plex than the true molars, by the form and position of the nasal bones and by the structure of the external nostril.