358 



Proceedings of the Royal Physical Society. 



following statement in the published abstract of Mr Davis's 

 paper : — " From the position of the respective maxillary and 

 premaxillary bones in this (Mr Davis's) specimen, there can 

 be no farther doubt that the small bifurcated bone of G. 

 aci;penseroides, Ag., described as the maxillary bone, is really 

 the premaxillary " (!). 



Fi.i 



iel 



-Profile of liead of Chondrostcus, restored. 



But if we inquire what this little " bifurcated bone " really 

 is, I answer that it seems to me to occupy, as regards the 

 maxilla and the great palate-plate, a position quite analogous 

 to that of the small bone in Acipenser lettered as " palatine " 

 by Professor W. K. Parker, but which I have come to look 

 •upon as a pterygoid or ectopterygoid, for the same reasons 

 which have induced me to regard the great palate-plate as a 

 mesopterygoid, and as such I have accordingly marked it. 



I have seen no evidence of ossified quadrate or metaptery- 

 goid elements. There can be no doubt that the bone inter- 

 preted by Sir Philip Egerton as a combined " mesotympanic " 

 and " hypotympanic " {symplectic and quadrate of modern 

 nomenclature), is that external plate appended to the hinder 

 extremity of the maxilla, which I have already described as 

 the jugcd. 



The mandible is stout, and anteriorly is, like the maxilla, 

 strongly curved inwards to meet its fellow of the opposite 

 side in a symphysis : its outer surface presents a well-marked 

 longitudinal groove, which approaches close to the superior 



