CHAPTER VII. 



ANALYSIS OF THE FAUNA. 



In attempting an analysis of the Permo-Carboniferous vertebrate fauna 

 of North America, several facts become at once apparent which are in entire 

 accordance with evidence furnished by the beds in which the remains are 

 preserved. 



There are )w forms which can be called distinctly marine. 



As is well known, there are several sliarks which live in brackish, or even 

 fresh, water (see p. 124). The dipnoans and crossopterygians are inhabitants 

 of fresh water. Correlatively it may be stated that bones of sharks and 

 fishes do not occur in the limestones of the Clear Fork beds associated with 

 marine invertebrates. In only a few places have bones of fishes or other 

 vertebrates been found in limestones, and these are indeterminate fragments 

 which might have been carried a long distance. 



Amphibians are generally able to live only in fresh water, salt water, 

 even when very dilute, commonly preventing development of the egg, and, 

 in more concentrated form, being fatal to the individual. A recent paper 

 by Pearse," however, reports the development of tadpoles in the waters of 

 a small creek entering Manila Bay. Three analyses of the water of this 

 creek give respectively 2.6, 2.1, and i.i per cent sodium chloride. Normally 

 0.6 per cent of sodium chloride is sufficient to prevent gastrulation of the egg.^ 

 The waters of this creek were subject to tidal influence, and so the quantity 

 of the sodium chloride undoubtedly varied, but it can hardly be supposed 

 that it was ever below 0.6 per cent for any length of time. 



Darwin" mentions that the tadpoles of certain frogs develop in sea-water 

 on the coast of India. 



Carl Wiman'* in 1 9 1 1 reported the discovery of some long-snouted forms 

 in the Trias of Spitzbergen, which he considered as marine amphibians. 

 Cossman has suggested, however, that these are possibly reptilian. 



Amphibians of to-day live in waters which contain an abundance of 

 dissolved salts, mostly calcium carbonate: as Proteus of the Austrian caverns, 

 and Cryptobranchus, etc., of the streams of the Mississippi Valley. 



These facts lend support, so far as they go, to the suggestion which has 

 freqiiently been made that the ancient amphibians may have been far more 

 tolerant to the effect of sea-water than living forms. On the other hand is 

 the fact that amphibian remains have never been found associated with 

 marine invertebrates in a way to suggest that they lived in the same waters. 



" Pearse, Philippine Journal of Science, vol. VI, No. 4, sec. D. 



■■ Glaser, Science, vol. 36, p. 679. 



' Darwin, Origin of the Species, 6th ed., p. 414. 



"* Wiman, Bull. GeoL, Upsala, 1911, vol. ix. 



