192 ANN ALU NEW YORK ACADEMY OF SCIENCES 



Dr. Gregory said in abstract: in a skeleton of the temnospondylous 

 amphibian, En/ops megaccphatus Cope, from the Permian of Texas, 

 which is now being mounted in the American Museum, the limbs are of 

 special interest, Many resemblances to the contemporary reptile Dia- 

 dectes are seen : in the stout, long coraco-scapula, the short, wide-headed 

 humerus, with its very wide, prominent and backwardly directed ento- 

 condyle, in the short fore-arm, in the very heavy, solid pelvis, stout 

 femur and fully ossified carpus and tarsus. In the character of its limbs, 

 Eryops was on the whole nearer to Sphenodon than to the TJrodeles, 

 though far more archaic than the former. As shown by the facets, the 

 humerus and femur were held almost at right angles to the body, the 

 opposite feet being held very widely apart. 



The generalized character of the limbs of Eryops with respect to those 

 of higher Tetrapoda invite renewed inquiry into the origin of paired 

 limbs from fins. The limbs of known branchiosaurs and microsaurs do 

 not carry us very far back toward any known type of fish fin. In these 

 orders, the cylindrical shafts of the long bones, with cartilaginous ends, 

 the cartilaginous carpus and tarsus, the weak shoulder girdle and pelvis 

 suggest a secondary adaptation to aquatic habits. 



From the work of Thacher, Goodrich, Dean, E. C. Osburn and others, 

 it seems probable that the paired fins of fishes, like the median fins, have 

 evolved from wide-based fins with serially arranged basal and radial 

 cartilages. After the formation of the primary shoulder girdle and 

 pelvis and of the pro-, meso- and metapterygia by fusion and growth 

 of the basals, the various types of paired fins seen in plagiostomes, chimaa- 

 roids, pleuracanths, dipnoans, crossopterygians and aetinoptervgians seem 

 to have arisen in each case through the protrusion of the basal cartilages, 

 differential growth and shifting of the radials, and in some cases (c f/.. 

 pleuracanths, crossopterygians, dipnoans) also through the extension of 

 the radials around to the post-axial side of the metaptervgial axis. If 

 the Amphibia have descended from forerunners of teleostomous and dip- 

 noan fishes (as seemed likely), then it was entirely probable that their 

 paired fins had been transformed into limbs through the extreme pro- 

 trusion of the proximal cartilages, differential growth and regrouping 

 of the more distal cartilages, reduction of the dermal rays. This struc- 

 tural change may well have been in large part effected before the air- 

 breathing proto-amphibians had left the water, owing to the assumption 

 of a new function in the paired fins, i. e., pushing against solid objects 

 such as roots in the stagnant water, instead of merely steering. A study 

 of the pectoral girdle and fins of Sauripteris, a rhizodont crossoptervgian 

 of the Upper Devonian, in comparison with those of Polypterus and with 



