| M. | |
| Breadth of frontal at postorbital process | ·045 |
| Breadth of frontal in front of postorbital | ·030 |
| Breadth of nasal just in front of orbit | ·032 |
| Length from angle of nares to end of premaxillary | ·1235 |
| Length of premaxillary | ·056 |
| Length of maxillary | ·230 |
| Breadth of palatine process at canine | ·026 |
| Breadth of palatine process at second premolar | ·029 |
| Vertical height of maxillary at angle of nares | ·064 |
| Breadth of maxillary across floor of orbit | ·058 |
| Fore-and-aft diameter of orbit | ·054 |
| Length of malar along maxillary | ·094 |
| Vertical diameter of malar behind maxillary | ·029 |
| Transverse diameter of malar behind maxillary | ·033 |
| Fore-and-aft diameter of glenoid cavity (about) | ·029 |
| Vertical diameter of squamosal at end of malar articulation | ·032 |
| Transverse diameter of squamosal at end of malar articulation | ·0325 |
| Length of ramus mandibuli from symphysis to ascending portion | ·177 |
| Depth of jaw at last molar | ·068 |
| Depth of jaw at second premolar | ·061 |
DENTITION.
Upper Jaw.—The incisors, three in number, are placed close together in a nearly straight line, which does not make so great an angle with the line of molars as in Palæosyops. They increase regularly in size from the first to the third, which is very large. They all have stout rounded fangs, and sharp pyramidal crowns, with strong basal ridges separated from the acute blades by deep clefts. Between the incisors and the canine there is a long diastema.
The canine is of great size; it has a swollen fang, and a long recurved crown which is much compressed, and has sharp serrated cutting-edges. The external face is the more convex, the internal has a well-marked basal ridge, and both are longitudinally striated. The canine is separated from the premolars by a short diastema.
Premolars.—The first premolar stands by itself, separated by a short interval from the second. It is implanted by two fangs, and has a compressed crown with sharp cutting-edges. It is nearly twice the size of the corresponding tooth in Palæosyops, which is simple and conical. In the specimen under description there is, besides the principal lobe of the tooth, a rudimentary anterior lobe which gives the crown an elongate shape. The basal ridge is shown on the inner side only. The second premolar has a crown which is oval in section. The external part consists of two sharp-pointed cusps, separated by a valley, but confluent at base; while the internal division is a low ridge (not a pointed cone as in Palæosyops) with a tubercle developed behind it. The basal ridge is marked all around, and sends up a buttress along the antero-external lobe; as is also the case in the third and fourth premolars. These are enlarged copies of the second; but have the internal lobe elevated into a sharp cone, and showing a much stronger basal ridge and deeper median valley. These teeth differ in several respects from the premolars of Palæosyops. The crowns are higher and the lobes sharper; the basal ridge is more distinct, and is not interrupted at the internal cusp; the external ascending buttress is stronger; and there is no fold between the external lobes of the fourth.
The molars are constructed in a manner which resembles that of P. paludosus rather than of P. major, but its resemblance to the form shown in Titanotherium is stronger than to either. They have broad, square crowns, which increase progressively in size from first to last. There is a convexity running up the median line of the external lobes, and the two posterior lobes are connected together at their bases. The first molar does not exhibit such a decided increase in size over the last premolar as is seen in Palæosyops; the two external lobes are more erect and sharper than in any form of that genus. The cingulum is complete even across the internal cones, and the median valley is very deep, as in Titanotherium. There is a conspicuous fold at the junction of the external lobes, and a minute tubercle between the two anterior lobes; this tubercle is present only in the first molar, and not throughout the series, as in Palæosyops. The second molar in general form is like the first; but is larger, has a deeper median valley, more conspicuous external folds, and a stronger basal ridge. There is also some change in the proportions of the crown; the first measuring the same in both directions, while the second is wider than it is long. The last molar has but one internal cone; the second is represented by a tubercle; which however is a true rudimentary lobe and not a development of the basal ridge. In this tooth, the external fold is very large and the median valley very deep.
Lower Jaw.—The lower molars and premolars are very much like those of Palæosyops, but are longer, narrower, and higher. The incisors are not at all like Palæosyops, but are compressed and laniariform, with acute crowns and sharp cutting-edges. The canine is not present in our specimen; but that it was large, is shown by the long diastema between the upper canine and incisors.
Premolars.—The first is small, simple, and implanted by a single fang close to the canine. The diastema between it and the second premolar is about one half of that in P. major. The second premolar is the most peculiar tooth in the lower series; as it carries the development of the anterior lobe at the expense of the posterior lobe, to a still greater extent than in Palæosyops., forming a crown like the blade of the carnivorous sectorial. The third lobe of the last molar is no longer a simple cone, but a functional lobe, with two crests running from it, which bound a median valley.
Teeth Measurements.