No. 1 8.] TRIASSIC FISHES OF CONNECTICUT. 21 



which compels us to regard the sediments in question as a non- 

 marine facies of the Trias does not proceed primarily from the 

 fossil fishes themselves. On the contrary, the North American 

 species of Semionotus, Ptycholepis, and Diplurus are so closely 

 affiliated with European " geminate types," to employ Jordan's 

 term,i which occur in the marine Trias, that it is impossible to 

 suppose that there were any great physiological differences be- 

 tween them. Hence there would be no reason in the absence of 

 other evidence to believe that that they were adapted to a diflferent 

 habitat.^. 



While there is nothing in the character of the fossil fishes 

 which would prove conclusively whether the deposits were 

 formed in salt or brackish or fresh water, the physical character 

 of the deposits and the fossils other than fishes found in them 

 make it substantially certain that the deposits are not marine.* 

 No corals, echinoderms, or brachiopods have been "found in the 

 Triassic in Connecticut or in any other of the Triassic basins 

 of eastern North America. Mollusks are very few, and most 

 of those found are undoubtedly fresh-water forms. A very few 

 marine mollusks, it is claimed, have been found in the Triassic 

 of Pennsylvania. A few Crustacea, probably fresh-water or 

 brackish-water forms, have been found in some of the southern 

 Triassic basins, though not in Connecticut. A few insect larvae 

 have been found. For the rest the fossils of the formation con- 

 sist of land plants and tracks of reptiles and amphibians, with a 

 few skeletons of reptiles. Such an assemblage of fossils makes 

 it clear that the formation is not marine, though the presence 

 of a few marine shells (if those shells are rightly identified) 

 indicate conditions in part estuarine. 



Until recently the opinion has been generally held that the 

 deposits of the Triassic of eastern North America were formed 

 in tidal estuaries whose waters for the most part were brackish 

 or nearly fresh. It seems probable, however, that the deposits 



1 Jordan, D. S., The Law of Geminate Species. Am. Nat., 1908, xlii, pp. 73-80. 



2 De-Alessandri remarks as follows regarding the conditions under which the strata 

 at Besano were deposited: " I caratteri litologici infatti dimostrano come i depositi 

 costituenti la formazione raibliana di Besano debbono in parte ascriversi ad azione ' 

 organica e che essi si costituivano poco lungi dalle coste. E I'esame della sua 

 ittiofauna .... conferma appunto la natura costiera del giacimento." 



8 Rice and Gregory, Manual of the Geology of Connecticut, pp. 166-179 (State 

 Geol. and Nat. Hist. Surv., Bull. 6.) 



