ILLUSTRATIONS 



12. — First Claimant to the Line of Ancestry 

 OF the Higher Vertebrates. Devonian 

 "Lobe-fin" {Eusthenojpteron) . . facing 23 



(Reconstruction by Bryant.) 



13. — Second Claimant to the Line of Ancestry of 

 the Higher Vertebrates. Devonian Dip- 

 noan (Dipterus) .... facing 24 



(Restoration by Pander.) 



14. — Embryos of Modern Lobe-Finned Fish (A) 



AND Amphibian (B) ..... 26 



A. Embryo of Polypterus bichir. (After Budgett.) 



B. Embryo of Amhlystoma punctatum. (After S. F. 

 Clarke.) 



15. — One of the Most Primitive Known Amphib- 

 ians (Eogyrinus) from the Lower Carbon- 

 iferous of England .... 28 



Restoration of skeleton. (Based on data of D. M. S. 

 Watson.) 



16. — Skull of One of the Oldest Known Amphib- 

 ians {Loxomma allmani) . . . facing 28 

 (After Embleton and Atthey.) 



A. Upper surface. 



B. Under side. 



17. — Skulls of Lobe-finned Fish and Early 

 Amphibian, Showing Loss of Opercular 

 Series in the Latter .... 30 



A. Lobe-finned fish, essentially Rhizodopsis. (From 

 data by Traquair and Watson.) 



B. Primitive amphibian, Paloeogyrinus. (After 

 Watson.) 



In the primitive amphibians the space formerly 

 covered by the opercular region was covered by the 

 tympanum or drum membrane. 



XV 



