506 



EDWIN S. GOODRICH. 



lation is thicker than the middle region of eacli segment, in the 

 case of the superficial fin-scales it is usually just the reverse, 

 the middle region of the scale being the widest (figs. 57 

 and 58). The only doubtful point is as to whether they are, 

 or are not, contiuuous below with the rays. I am strongly 



fui-.f: 



-^.4C. 



..e.ie. 



Tig. 6. — Diagrammatic section tlirough tlie dorsal fin of Dipterus. 

 For lettering see p. 517. 



of the opinion that they are not. A section of the fin show- 

 ing the scales above and the camptotrichia below would, of 

 course, clinch the argument in favour of Pander's view ; but 

 such a decisive section I have, unfortunately, not been able 

 to obtain for lack of suitable material. 



The dermal rays of Dipterus are formed of bone with 

 numerous branching cells, very like those of Ceratodus 



