PROFESSOR OWEN ON THE AYE-AYE. 49 



are straight lengthwise, convex across, and the more so as they approach their free ends ; 

 they join above with the frontals (ib. "), and at the sides with the premaxillaries (ib. 22;. 

 The presphenoid is short, smooth on the under surface, and concave there transversely. 

 The vomer quickly assumes the form of a vertical plate, with the free hind border 

 concave. 



The palatines form the hinder third of the bony palate ; the suture of each with the 

 maxillary is slightly convex forward : they are divided from the inner alveolar wall of 

 the last two molars by a groove which deepens into a fissure, bounded beyond the last 

 molar by the pterygoid (PI. XX. fig. 2). The maxillary forms more than the middle 

 third of the palate, leaving the smallest share of the roof of the mouth to the pre- 

 maxillary (ib. 22). The facial plate of the maxillary (PI. XlX. 21) extends by a 

 narrow produced apex to the lacrymal, but is excluded from the frontal by the 

 junction of the lacrymal with the premaxillary ; it is, transversely, convex at its 

 outer, concave at its inner or fore part, both in a slight degree ; its middle is per- 

 forated by a small antorbital foramen ; its hinder angle is produced a little way beneath 

 the molar. The anterior half of the alveolar border is edentulous, but sharp : the 

 posterior half is excavated by the sockets of the four grinders ; of these sockets the 

 first is the smallest, and is a simple cavity ; the second (PK XX. fig. 8, "■ ■) divides into 

 three depressions for one large inner and two small outer fangs ; the like divisions of 

 the third socket (ib. "• 2) are less deep ; the fourth socket is simple, larger and more 

 oblong than the first. These four sockets are in a straight line and parallel with those 

 of the opposite maxillary. 



The premaxillaries (PI. XIX. 22) constitute a larger share than the maxillaries to the 

 facial wall ; on the palate they form merely the fore and outer boundaries of the incisive 

 fissures (PI. XX. fig. 2, 0), and extend only one line behind the incisors. On the face 

 they reach the frontals, rising as high as the nasals, between which and the maxillaries 

 they interpose a broad plate, circumscribing, with the nasals, the external nostril. The 

 socket of the incisor curves upward and backward to the maxillary, in which it is con- 

 tinued to beneath the orbit. 



The malar bone (PI. XIX. as) is long and deep, especially below the orbit, of which 

 it forms the lower half; and where it bends outward to expand that cavity, it unites with 

 the lacrymal and extensively with the maxillary anteriorly, and bifurcates behind, — 

 the narrower branch (PI. XX. fig. 4, 26) mounting to the postorbital (ib. 12), the broader 

 one {ib. fig. 2, 26) continuing backward to the squamosal {ib. 27). 



This essentially facial or maxillary element (Pis. XIX. & XX. 27) is anchylosed not 

 only with the mastoid (s) and petrosal (>6), but also with the tympanic {"-<>) ; its cranial 

 plate forms the outer and back part of the depression for the natiform protuberance 

 (PI. XX. fig. 5, 27), and terminates by a convex upper border overlapping the contigu- 

 ous borders of the alisphenoid and parietal (PI. XIX. 27). The surface for the mandible 

 (PI. XX. fig, 2,x) is broad and flat, save where its inner border bends down upon the 



VOL. v. — PART II. H 



