24 ,PEOF. OWEN ON THE SKTJLL OF AKGILLOENIS LONGIPENNIS. 



part and the lower end of the bone are broken away on both sides. 

 The praelacrymal vacuity (fig. 1, Z) is arched above, and slightly ex- 

 panded , at the lower base, which is made straight by the narrow 

 maxillo-malar bar, 21-26 ; from this is continued a small portion of 

 the suborbital part of the malar. 



The constituents of the preserved basal portion of the upper man- 

 dible have coalesced into a bony roof, sloping from a ridge-piece, 

 which soon becomes narrow as it advances from the fronto-nasal 

 suture, 11-22. The short horizontal tract beyond the suture is di- 

 vided from the sloping sides by a pair of low, short, oblique ridges 

 (fig. 2, 15, 15), continued from the ends of the suture obliquely forward 

 and inward. The roof gradually narrows from a basal breadth of 

 1 inch 6 lines to one of 11 lines, where the snout-end of the upper 

 bill is broken away. 



The sloping sides in advance of the ridges, 21, 22, fig. 1, are feebly 

 concave along the upper half, and as feebly convex toward their 

 lower border, which is traversed a little above the alveolar margin 

 of the upper jaw by a longitudinal groove (fig. 7, g). This margin 

 is broken away on both sides, and large cancelli of pneumatic cha- 

 racter are exposed. 



At one short tract on the right side (ib. /), which appears 

 to be the uninjured alveolar border, there are the outlets of four 

 small vertical pits, like the sockets of teeth, but filled with matrix. 

 Of this portion a magnified view is given at fig. 7 a, PL II. The 

 part is, unfortunately, wanting on the opposite side, and along the 

 rest of the fractured alveolar borders on the right side (fig. 7) of the 

 upper mandible. The fractured fore end. exposes a nasal cavity, 

 n, fig. 4, below which is the widely cancellous structure of the 

 palatal floor, beneath the middle of which, in a longitudinal groove, 

 is a small portion of bone, p. 



The fractured cancellous tracts of the alveolar borders of the 

 upper biU I take to be the base of those borders which, when entire, 

 contracted to a narrow margin, possibly dentigerous, and were divided 

 from the palatal surface by a longitudinal groove, the mesial side of 

 which was continued into a palatal tract, descending some way 

 below the alveolar border, and terminating in the ridge bounding 

 the side wall of a long and narrow mesial palatal vacuity — the 

 palato-naris (fig. 3, pn). The suture indicating the proportions 

 respectively contributed by the maxillary and palatine bones is 

 well marked on both sides ; and, after a course from behind for- 

 ward of 15 millims., the fore end of the palatine underlaps the 

 broadening part of the maxillary plate. In advance of the pala- 

 tines, the maxillo-praemaxillary portion of the palate is a continuous 

 roof of bone, longitudinally grooved at the mid line, at the fore end 

 of which is the fragment of bone above noticed. The exposed palatal 

 surface of the palatine gradually expands to a breadth of 10 millims., 

 and as gradually contracts to where it changes the horizontal for the 

 vertical direction, bending forward anteriorly to bound the palato- 

 naris, and thence continued backward to apply itself to the inner 

 side of the fore part of the pterygoid, 24. The length of the palatine 



