Manchester Memoirs, Vol Ix. (191 6), No. % 33 



Several of our specimens show quite clearly the 

 presence of pre-vomers, which overlap the anterior ends 

 of the pterygo-palatines, passing back between the ends 

 of the large crushing " teeth " for some distance. They are 

 quite large bones of somewhat feeble structure, and bear 

 at least two and possibly three transverse rows of very 

 small bluntly-pointed teeth. Anteriorly they reach for- 

 ward to the lower edge of the cranial shield, with which 

 they articulate in some way which our material does not 

 clearly explain. We have observed a single row of 

 similar small blunt teeth on the lower margin of the 

 cranial shield between the notches which mark the 

 position of the nostrils. These show that that region is 

 really formed by the premaxillae. 



The chief new features of importance shown by these 

 specimens are those of the brain case. The evidence 

 seems to us conclusive that the fusion of spinal elements 

 with the back of the skull, which is so marked a feature 

 of Ceratodus and which Barkas has shown to occur in 

 Ctenodus, had already begun in Dipterus, although the 

 parasphenoid had not at that time developed the re- 

 markable posterior projection lying below the anterior 

 part of the vertebral column which it subsequently 

 acquired. Another striking feature of the brain case 

 already noted by Traquair is its extraordinary complete 

 ossification. The vomerine teeth of Dipteriis have been 

 previously figured by Goodrich in a restoration but are 

 not quite accurately represented by him. Hussakof has 

 figured vomerine teeth in Scaumenacia, but we shall show 

 later that it is possible that these really belong to the 

 premaxillae, although his identification may very probably 

 be correct. The occurrence of a definite series of pre- 

 maxillary teeth is interesting, as the similar teeth in the 

 dentary were described by Traquair long ago. 



