1857.] OWEN PLIOLOPHUS VULPICEPS. 57 



The mandible, 29, 30, had been dislocated, about 4 lines in advance of 

 its place of articulation, prior to the consolidation of the surrounding 

 matrix, by which it is now fixed with the lower teeth to the same 

 degree in advance of their correspondents above, as in PL II. fig. 3. 

 This dislocation enables the flattened surface of the major part of 

 the glenoid cavity to be brought into view, at g, fig. 3. In figure 4 

 the mandible is figured as in its proper position. 



The ascending ramus of the mandible developes a short recurved 

 coronoid process, PL II. fig. 4, r ; below this and the condyle d, it 

 expands, gradually extending backward as it descends from the 

 condyle, describing an irregular convex curve as it passes into the 

 under border, and forming a broad angular plate, 29, for the implant- 

 ation of the pterygoid and masseter muscles. The fossa indicating 

 the insertion of the temporal muscle, fig. 3, t, is limited to the upper 

 half of the ascending ramus, where it is bounded by a curved line or 

 bank continued downward and forward from the outer part of the 

 condyle : the anterior border of the depression subsides upon the 

 part of the jaw which extends outward from the alveolus of the last 

 molar. The outer side of the horizontal ramus of the mandible is 

 lightly convex : the lower border, continued from the broad rounded 

 angle, is at first gently concave, then as slightly convex. The ramus 

 very gradually decreases in depth to the first premolar, below which 

 the symphysis begins, PL II. fig. 1, s, i. Here the mandible is a 

 little compressed and again expands slightly to form the alveoli of 

 the canines, c, and incisors, i, 1, 2, 3. The line of the symphysis 

 rises very gradually to the incisive border, s i, figs. 1 and 2, PL II. 



The following traces of sutures are unmistakeable : the squamous, 

 PL II. fig. 3, q, continued forward from the irregular depressions 

 on the side of the cranium, at first straight, then with a downward 

 curve ; the straight part is 9 lines below the sagittal crest, 7 : the 

 interfrontal suture, PL II. fig. 2, 11, continued into the internasal one, 

 ib. 15, along the midline of the facial part of the skull : the fronto- 

 nasal suture, ib.f, describes a slight sigmoid curve, as it extends 

 transversely outward and downward to the lacrymal, 73, fig. 3, PL II. 

 The suture connecting this bone, 73, to the maxillary, 21, and malar, 

 26, shows that its facial plate is about 4 lines in vertical, and 3 in 

 fore-and-aft, diameter. The malar, 26, forms the lower half of the 

 fore part of the orbit ; the anterior end of its almost horizontal suture 

 with the squamosal, 27, begins just below the postorbital process. 

 The naso-maxillary suture, PL II. figs. 3 and 4, m, is nearly straight, 

 1 inch in length ; its continuation by the naso-premaxillary suture n 

 is about 6 lines in extent ; but this part of the lower border of the 

 nasal, 12, is slightly convex downwards, with a corresponding curve 

 of the suture. The maxillo-premaxillary suture, p, is almost a straight 

 line, parallel with the lateral border of the nasal aperture. 



The following are admeasurements of the skull of the Pliolophus, 

 with some comparative admeasurements of that of the Hyracothe- 

 rium : — 



