042 



THE AMERICAN NATURALIST [Vol. XLIX 



squamosal, quadrate, pterygoid, 

 palantine, supratemporal, para- 

 sphenoid, postorbital. Ethmoid 

 present in Gymnophiona. 



VIII. Pineal opening present 



X. No air bladder. Lung an- 

 lagen on ventral surface of phar- 

 ynx. 



XL Pelvic girdle composed of 

 osseous ilium, ischium and car- 



XII. Arm consisting of hu- 



times cartilaginous), metacarpals 

 and phalanges. 



XIII. Leg composed of femur, 

 tibia, fibula, tarsus (sometimes 



phalanges. 



XIV. Ribs single, long or 



XV. Form of body not fish- 

 like. 



XVI. Mesonephros functional 

 in adult. 



XVII. External gills slender 

 and thread-like in the young of 

 all living and some of the ancient 



Pectoral fin composed of pro-, 

 meta— , and mesopterygium, acti- 

 nosts and fin rays. Broom (2) has 

 correlated the elements in the arm 

 of Sauripteris taylori with those 

 of the amphibian arm down to the 

 actinosts, which he regards as car- 

 pals. The fin rays would repre- 

 sent phalanges. 



Pelvic fin composed of basiost 

 which represents the femur, and 

 meta- and mesoptergyia and fin 



Ribs double; dorsal, arising in- 

 dependently of transverse proc- 



process of vertebra, which in the 

 tail becomes the hajmal arches by 

 fusion of the tips. 



Form of body always typically 

 fish-like. 



Mesonephros functional in adult, 

 thread-like, recalling those of lar- 



It will be seen from the above list of comparative struc- 

 tures that there are a variety of instances in which the two 

 groups approach each other. It is, however, to be clearly 

 kept in mind that the oldest known Amphibia, as indi- 

 cated by our present knowledge of these forms, are more 

 like the modern forms of Amphibia than they are like 

 the ancient types of fishes from which they supposedly 

 have been derived. In other words, a more complete 

 knowledge of the Coal Measures Amphibia has not served 

 to simplify our ideas of amphibian descent in the least, 

 but rather to confuse them. 



All of the early Amphibia have well-developed ambula- 

 tory or natatory limbs and none of them are fish-like in 



