258 TEN years' progress in vertebrate paleontology 



ago. Very much yet remains in the completion of our knowledge of old 

 things, and when things are well known, he who runs may read. 



Among fishes, of which I can speak but briefly, perhaps the most far- 

 reaching, if not important, result of the past ten 3'ears has been the 

 practical demonstration of the Thacher-Mivart-Balfour theory of the 

 origin of limbs from lateral dermal folds ; and this is especially pleasing 

 to me, since it is to a dear friend and colleague, the late Professor 

 Thatcher, that the credit for the conception of this theory is chiefly due. 



The recapitulation theory, to which the paleontologist yet gives full 

 faith, has been strengthened by the discoveries among elasmobranchs and 

 ganoids ; and, to use the words of Eastman, "extensive • series of pro- 

 gressive modifications have been traced among the cochliodonts, and 

 others, still more remarkable, among the so-called Edestidae." AATiile 

 the affinities of the i^rthrodira are still the subject of an animated 

 discussion, we may rest confident that their final disposition is almost in 

 sight. That they are no longer united with the Dipnoi is at least one 

 important step. 



To the bystander there are few things in vertebrate paleontology .of 

 more profound interest in the evolution of the vertebrates at the present 

 time than the relations of these forms which stand along the border 

 lines of the higher types. The affinities of the dipnoans and crossoptery- 

 gians to the higher air-breathers, the role in general that the ganoids 

 have played, the many problems yet awaiting solution among the elasmo- 

 branchs, all have an importance second to none others in the evolution of 

 the vertebrates. 



Among the Amphibia the discoveries of the past few years have been 

 none the less important and far reaching, ^liile, unfortunately, the 

 immediate relations of this class to the lower Anamnia are still involved 

 in great obscurity, we have a more confident expectation than ever before 

 of the early solution of their chief problems. The field is still one of 

 speculation, sometimes crude ; but speculations are at least useful in their 

 demolition. The phylogenetic relations of the modern amphibians with 

 the early stegocephs have become more intimate l)y the recognition of a 

 Urodele in the early Permian and an Anuran in the Jurassic; their di- 

 rect ancestry from the Branchiosaurs has been placed on firmer grounds, 

 if not established. The Microsauria l.ave lost much of their former 

 coherency, their relationships on the one hand with the true reptiles, on 

 the other with the true amphibia, more demonstrable. The temnospon- 

 dyls have established their genetic relationships beyond a doubt with the 

 reptiles, and for the first time the practically complete structure of any 

 member of the order has been made out ; the structure of their carpus 



