Manchester Memoirs, Vol. Ix. (1916), No. %. 23 



suggests that the squamosal has arisen from a more 

 complex arrangement and is really formed by the fusion 

 of the squamosal of Holoptychius with the other bones. 

 This view is supported by the fact that in the obviously 

 closely allied forms Tristichopterus and Eusthenopteron 

 the same region is in the British form covered by three 

 plates which are replaced by a single one in that from 

 Canada. It is therefore not improbable that extensive 

 fusions may have taken place between the bones of the 

 head of Rhipidistians, a view which seems to receive 

 additional support from the condition shown in the 

 fronto-ethmoidal shield of these fish. The same line of 

 argument will suggest that the small element which, in 

 Holoptychius and Glyptopomus lies between the squamosal 

 and the tabular, has in the probably more advanced forms 

 fused with the operculum. 



We have been fortunate in that our material has 

 allowed us to describe, imperfectly it is true, the structure 

 of the palate of two of these fish, a region which has 

 hitherto been practically unknown. The most striking 

 features of this palate are : — 



(1) the presence of a single very large pterygoidal 

 element which reaches back to clasp the posterior 

 surface of the quadrate and extends so far forward 

 as to articulate with the pre-vomers. 



(2) the fact that in Glyptopomus this pterygoidal 

 element articulates directly with the sides of the 

 parasphenoid. 



(3) that the pre-vomers are bones in the palate bearing 

 large fangs. 



(4) that there are distinct ectopterygoids and palatines 

 bearing a row of teeth which may be represented 

 only by a few large laniary teeth 



(5) that the outer edges of these bones are directly and 



