EVOLUTIONARY EVIDENCES 259 



and tarsus, if not feet, has been eventually determined. More important 

 than all these, perhaps, is the nearly complete demonstration of the Cope 

 theory of the origin of holospondylous vertebrae from the temnospondylous, 

 by the discovery of forms that are almost the missing links, forms that 

 seem to demonstrate the absolute morphological identity between the 

 intercentra of the modern reptiles and the hypocentra of the ancient 

 amphibia. 



The progress in our knowledge of the Eeptilia, at least so far as the 

 broader problems of phylogeny (and by phytogeny I mean evolution) are 

 concerned, has been perhaps greater than in any other class of vertebrates 

 during the past ten years — a progress which while it has cleared up many 

 things has involved others in great obscurity. One by one the characters 

 distinguishing this class from the Amphibia have been broken down, 

 till but few remain. The greater size of the pterygoidal vacuities of the 

 palate and perhaps the presence of a distinct intermedium pedis are the 

 last and only characters peculiar to the Amphibia now remaining. 

 Indeed, so closely allied are the forms already known that it is possible 

 to distinguish finally the skeleton of a cotylosaur from one of a tem- 

 nospondyl, only by the structure of the palate, the reduced size of the 

 intercentra, and the fused intermedium of the tarsus. But an actual 

 connecting link has not yet been discovered; the true microsaurs have 

 complicated the problem and thrown back the actual divergence of the 

 classes at least as far as the early Pennsylvanian. 



On the olher side, perhaps the most interesting of all the evolutional 

 advances iu paleontology- that have been made during the past ten years 

 is the practical demonstration by Broom of the origin of the mammalia 

 from the theiiodont reptiles. Xearly every distinguishing character 

 between these two classes has now been bridged over — the double occipital 

 condyle, the false palate, heterodont teeth, reduced and almost vestigial 

 quadrate and mandibular bones, the pectoral and pelvic girdles and the 

 feet. 



The primitive reptilian foot, dating from the middle Pennsylvanian, 

 first made kno\vn by Cope, has been established, a foot differing l)ut little 

 from that of the modern Sphenodon. 



Within the reptile class itself, among the most striking evidences of 

 evolution that have been presented in late years are those of the ich- 

 thyosaurs by Merriam. While unfortunately they throw no new light 

 on the ultimate origin of the order, his observations have shown clearly 

 some of their chief lines of evolution ; and of nearly equal importance are 

 the evidences produced in recent years of the derivation of the mosasaurs 

 from the terrestrial forebears of the modern monitors. I know of no 



