106 TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



s.or- 



B 



ant. orb. 



D 



Fig. 8. Comparison of skull patterns. 



A. Primitive palaeoniscoid, Cheirolepis. 



B. Primitive crossopterygian, Ostrolrpis. 



C. Primitive tetrapod, Palaogyrinus. 



D. Primitive dipnoan, Dipterus. All after Watson. 



