﻿WEALDEN FORMATIONS. 5 



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 Pterodactylus longirostris, the teeth of Pter. sagittirostris are subsimilar, divided 

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

 tively shorter than in Pter. crassirostris? and more resembling in disposition the indica- 

 tions given by the sockets in the portion of upper jaw of the Cretaceous Pterodactylus 

 compressirostris. 



The dentary bone supporting the above-numbered teeth is slender and subcompressed ; 

 its depth is given in figs. 1, 2, and 4 (nat. size) ; its thickness is shown in fig. 3. 



This is the same at both upper and lower borders, which are similarly rounded off ; 

 it is less half way down, owing to the concavity, vertically, of the inner surface of the 

 ramus (ib., fig. 4). The outer surface (fig. 1) is nearly flat ; it is traversed lengthwise by 

 a linear impression, which is 5 m.m. below the upper border at the hind end of the pro- 

 portion of the ramus figured in fig. 1, and is 7 to 8 m.m. below the outlets of the 

 sockets of the teeth 7 — 9. This linear impression does not indicate a suture. 



The ramus slightly increases in thickness, with a gain of convexity externally and a 

 deeper concavity internally (both being in the vertical direction), at the fractured end 

 (ib., fig. 1,32) nearest the symphysis. At the opposite end the angular element (ib., 

 fig. 4, 30) forms the inwardly prominent lower border ; the line between which and the 

 thin flat splenial forms (ib., ib., 3l) is clearly sutural. 



The portion of the right dentary preserved (PI. II, figs. 2, 3) answers to that 

 containing the sockets of the teeth numbered 2 — 9 in fig. 1. There is the same 

 obscurity or lack of demonstration of a socket or tooth behind the socket 2. 



The bases of the teeth are preserved in the sockets (numbered 2 — 6), and partly 

 project from the sockets 2 and 3, but the sockets 7, 8, 9, are vacant. 



The articular portion of the right ramus (figs. 5, 6, 7) lacks the prominent, backwardly 

 directed, end of the subangular (30)- 



1 Monograph above cited, Pal. Soc. vol. for year 1851, PI. XXVII, fig. 1. 

 3 Ib., ib., figs. 2 and 3. 



