METEIOElirNCHUS. 153 



as running from the maxilla on to the palatine. Behind this the palatine unites for 

 some distance with the maxilla, then, separating from it, forms the inner border of the 

 suborbital vacuity. It widens out a little towards its posterior end, which terminates 

 in an outer longer process and a shorter median one which unites in the middle line 

 with its fellow of the opposite side, projecting backwards from the ventral border of 

 the narial opening, which is thus divided into right and left halves. In specimens 

 figured by Deslongchamps * the ventral border of the narial opening is shown as 

 pointed anteriorly, the palatines being separated posteriorly by a notch : this is 

 not the case with the specimens here described. Anteriorly the upper surface of 

 each palatine is deeply grooved for the floor of the narial canal, which is separated 

 from its fellow of the opposite side by the vertical plate of the vomer (text-fig. 59, i). 

 A little further back there rises from the upper edge of the palatine a dorsal plate 

 (text-fig. 59, 2, 3) sloping up to the vomer, which it overlaps, completing the nasal 

 canals superiorly; the dorsal plate is concave from side to side. At about the middle 

 of the palatine the narial canals seem to have curved inwards and the dorsal plate of 

 the palatine is thickened and united above with the downwardly directed process of the 

 prefrontal and lachrymal. As Mr. Leeds has pointed out, the ventral process of the 

 prefrontal in modern Crocodiles unites with the palatine and pterygoid at the anterior 

 end of the latter and considerably behind the small vomer. 



The bone described by Mr. Leeds as the vomer (v.) is a large median element without, 

 as he pointed out, any trace of division into two lateral halves, a circumstance which, 

 taken together with the fact that it extends back to and unites with the ventral face 

 of the basisphenoid, makes it very probable that this element should rather be regarded 

 as a parasphenoid, the bones which are called vomers in the recent crocodiles being 

 absent, or at least not yet certainly recognised. At its anterior end the bone is 

 T-shaped in section, the vertical arm resting on the line of union of the palatines (text- 

 fig. 59, 1) and forming a median wall between the nasal canals; the upper surface is 

 grooved, the lateral arms of the T curving upwards to an increasing extent as they are 

 followed backwards, till opposite about the middle point of the palatines they enclose 

 a deep channel, and at the same time are considerably thickened (text-fig. 59, 2). The 

 upper edges of the dorsal plates of the palatines rest against the outer part of the 

 lower edge of these thickened arms of the T, which further back still, curve downwards, 

 the median groove disappearing (text-fig. 59, 3). Posteriorly the dorsal plates of the 

 palatines diverge from the vomer (text-fig. 59, 4), the roof of the narial canal being 

 completed by the anterior ends of the pterygoids. Behind this the vomer narrows and 

 is prolonged backwards between the pterygoids on the roof of the narial opening, 

 where it forms a median ridge. A similar ridge occurs on the roof of the narial 

 opening in a skull of Mystriosaarus from the Lias of Whitby, but it is not clear 



* Notes Paleontologiques, pi. xx. 

 PART II. X 



