﻿Vol. 64.] METRIOBHYNCHUS BRACHYRHYNCHUS. 353 



Q = Quadrate. 



S = Sphenoid. 

 TF = Temporal fossa. 



J = Jugal. 

 PT = Pterygoid. 



V = ' Vomerine element.' 



Explanation of Fig. 1 (p. 352), 



PN = Posterior nares, 

 P = Palatine. 

 M = Maxilla. 

 F = Frontal. 



Dotted lines on palatines = 

 Anterior extent of ptery- 

 goids. 

 Shaded portion of pterygoids 

 = Probable restoration 



PrF = Preelrontal. | posteriorly. 



[The maxillae are represented slightly crushed inwards, as in No. 165, 

 in order to include the jugals in the figure.] 



supeixiliosus obtained in the Peterborough district, these bones are 

 very rarely found in sufficiently-good preservation to allow of their 

 being restored in their entirety, partly on account of their thinness. 

 It is to the general massiveness of the skulls of M. hrachyrhynchus 

 here described that we owe the possibility, in the present instance, 

 of reconstructing these bones out of the numerous fragments in 

 which they were excavated. 



The palatines present the same truncated suture at their 

 junction with the maxillae, the two long gutters, and the vaulted 

 central portion without any marked keel, which Deslongchamps 

 noted. Posteriorly they widen and flatten out, until at a distance 

 of 215 millimetres from their anterior end they bifurcate, the 

 outer rami being the longer by about 15 mm., the intervening 

 notches limiting anteriorly the exits of the posterior nares. The 

 palatines have a sutural junction with the maxillae laterally of 

 about 115 mm. Their total length is 265 mm. 



In consequence of the bifurcation of the palatines posteriorly, 

 the opening of the posterior nares anteriorly is also bifurcate. 

 Deslongchamps figures it, in the case of other Metriorhynchidae, as 

 pointed anteriorly ; but in M. hrachyrhynchus^ at any rate, this is not 

 the case, as the palatines are united in the median line throughout 

 their length. However, as the median rami of the palatines are 

 somewhat slender, it is possible that they may not have been pre- 

 served in Deslongchamps's specimens. M. super ciliosus, as found 

 near Peterborough, shows the same disposition of the posterior 

 palatine border as Metriorhynchus hrachyrhynchus. 



In skull No. 165 the greater part of the palatines has been left 

 detached from the rest of the skull, to admit of examination of the 

 inner aspect, which is very well preserved. It shows the vomers in 

 position, forming with the palatines the nasal canals. Anteriorly 

 the canals occupy the whole width of the two bones (fig. 2, 1, p. 354), 

 having an outer wall and a median ridge with a curved intervening 

 surface. Very soon, however, the canals commence to converge 

 towards the inner half of the bones. At the point of convergence 

 the outer walls rise and become more massive where the deflex 

 processes of the praef rentals meet them to support the frontal 

 region (fig. 2, 2). In recent skulls which I have examined, these 

 processes meet the palate at the junction of the palatines and 

 pterygoids, and the vomers are situated forward of this point. In 

 Metriorhynchus thev appear to have been in contact with the 



2a 2 



