146 Evolution and Distribution of Fishes 



As the author then well remarks: "not one of the above- 

 quoted species occurs in any of the lists which I have given 

 from the Calciferous Sandstone Series of the district, while 

 all of them except Harpacanthns fimbriatus are well known 

 from the Mountain Limestone of England, and except 

 Pristodus falcatus, of Ireland likewise." It will be noted 

 also that the above list consists wholly of elasmobranchs. 

 From abundant evidence advanced by several of the British 

 palaeontologists however, it is evident that a few of the 

 hitherto inland fishes, and also these elasmobranchs were be- 

 coming anadromous, or even had become wholly littoral 

 marine species. Previous papers by Traquair (9^: 1:34; 

 g^: 2:540) as well as subsequent ones support a like con- 

 clusion. 



A richly fossiliferous set of Scottish Calciferous rocks 

 is met with in the Eskdale-Liddesdale region. Peach, 

 Kidston, and Traquair have jointly studied its organisms. 

 Freshwater crustaceans, eurypterids, and scorpions, as well 

 as 28 species of fish were listed. Kidston, in discussing the 

 fossil plants, joins hands with Peach in emphasizing the 

 striking similarity of the organisms they studied, to a set 

 from Illinois studied by Meek and Worthen. 



But that fishes were by no means the most highly evolv- 

 ed animals of the Calciferous age is proved by Huxley's 

 description of the Amphibian Pholiderpeton from the Forth 

 basin, while the other genera described by him from Ireland, 

 give proof that during the Old Red period, certain derivative 

 descendants from some group of the fishes, had already 

 become by degrees evolved and modified up to the amphi- 

 bian stage. The writer has already claimed that the direct 

 line of ascent is to be sought for in types allied to the 

 cyclostomes; from these intermediate organisms probably 

 led to primitive representatives of the Amphibia apoda, 

 thence to simpler, and later to more evolved, Urodela. 

 The writer fully realized, when the claim was made, that 

 very slight palaeontological evidence existed in favor of 

 such a view. But the serious gap has been considerably 

 bridged over since, and this most perfectly by recent publi- 

 cations of the Carnegie Institution. Most suggestive is 



