540 BRITISH FOSSIL REPTILES. 



fig. 8, m) in their natural relative position, the angle of convergence is shown ; and this 

 affords a ground for estimating the length of each ramus from the articular surface to the 

 hind part or border of the symphysis at 13 inches, the extent beyond remaining 

 conjectural. 



The specimen includes a portion of the left ramus, 9 inches 8 lines in length (of 

 which the anterior 7 inches are given in PI. 18, fig. 1), and two portions of the right 

 ramus, of which the dentary part measures 5 inches (ib., fig. 2) in length, the articular 

 part 2 inches (ib., fig. 5). 



The portion of the left ramus includes the dentary element (ib., fig. 1, and fig. 4, 32) 

 with the anterior part of the splenial element (fig. 4, 3i). The dentary includes ten of the 

 hinder sockets (ib., fig. 1, i, 2, 3, 4, 0), of which the five foremost (ib., 6, 7, 8, 9, lo) retain 

 more or less of their teeth. As the number of these which may have been present in the 

 fore part of the jaw is unknown, I count those which are preserved from the hind end of 

 the series forwards. Prolonging the alveolar border according to a moderate estimate of 

 the symphysis, and supposing the teeth to maintain the same intervals, about eighteen 

 may be assigned to each ramus. 



The border of the hindmost socket (fig. 1, 1) is not prominent as in the rest, and there 

 is room for doubt whether the oval vacuity which indicates the hindmost tooth really 

 contained one. There is none, however, with regard to the next socket (ib., 2), for tiiis, 

 like the antecedent ones, rises at its outlet above the level of the surrounding part of the 

 bone. It projects from the onter part of the thick, transversely convex, upper border of 

 the dentary, and the course of the cavity shows that the tooth must have inclined some- 

 what outward as well as forward from the perpendicular. The long diameter of the 

 outlet is in the axis of the jaw, and is 1^ lines (3 m.m.). The short or transverse diameter 

 is 1 line (2 m.m.). The interval between this socket and the one marked 3 is 5 lines 

 (10 m.m.). 



The prominent outlet of the socket 3 gives 5 m.m. in long diameter and 3 m.m. in 

 short diameter ; these dimensions with that of the interval are repeated to the socket 

 6, which retains its tooth. The exserted crown of this is 5 lines (10 m.m.) in length; it 

 is conical, acute, gently curved, with the convexity outward and forward. 



The apex of the next tooth in advance is broken off", but the basal half is better 

 cleared out of the matrix, giving an antero-posterior breadth of its issue from the socket 

 of 5 m.m. 



The teeth in the sockets 8 and 9 are better preserved, and show well the characters 

 of the mandibular ones in the present species. 



As in Pterodadylus longirostris, the teeth of Tter. sagittirosiris are subsimilar, divided 

 by nearly equal intervals, these being somewhat wider than in Pter. longirostris} rela- 

 tively shorter than in Ptcr. crassirostris," and more resembling in disposition the indica- 



1 Pterosaurin, P\. l,fig. 1. 



2 lb., lb., figs. 2 and 3. 



