ON MEGALICHTHYS 327 



nature of the decorticated bone and in the arrangement of the 

 cranial roof-bones Megalichthys exhibits close affinities with 

 this Amphibian group. Similar affinities have been shewn to 

 exist between Rhizodopsis and Pelosaurus, but an additional 

 point of resemblance is furnished by the paired nuchal plates 

 of Megalichthys (text-fig. 3A). 



Although it has been urged that the Crossopterygian brain 

 is retrograde in character, and that the cerebral cortex of 

 Dipnoans is an indication that brain evolution took place 

 through that group, it must be borne in mind that living 

 representatives of the order fall outside the Rhipidistia, and 

 that retrogression of one genus or sub-order is no criterion in 

 this matter, but is a feature which is natural in a late repre- 

 sentative of a group in which rapid evolution took place at an 

 early period of its history. 



From a consideration of the relationships of Megalichthys it 

 is clear, then, that the position of the fish in the family 

 Osteolepidae is by no means secure, and that there are indica- 

 tions that the classification of Rhipidistia, in part at any rate, 

 is premature and consequently unsatisfactory. Although 

 Megalichthys is not itself the ancestral type of the Stegocephalian 

 Amphibia, there can be little doubt that the study of this 

 genus leads inevitably towards the conclusion that its affinities 

 are with the ancestral type, and that the Stegocephalia were 

 evolved from a similar fish and probably from a nearly related 

 form. 



%* I wish to express my thanks to all who have helped 

 me, but especially to Dr. Hickling for advice from time to 

 time, and to the authorities and staffs of the Manchester, 

 Hancock, and Leeds Philosophical Society's Museums for 

 giving me access to material and facilities for research. 



Since I submitted my paper to the Society Mr. Gill's help 

 in preparing illustrations, as well as in arranging for the* 

 printing of the text, has been invaluable. To him also I offer 

 my best thanks for this additional kindness and courtesy. 



