GUELPH FAUNA IN THE STATE OF NEW YORK I I J 



of the Red sea learns that in the numerous cavities and in the small ponds 

 between the masses of seaweed there is displayed an overwhelming variety 

 of small gastropods, echinoderms, lamellibranchs and crustaceans. The 

 gastropods are evidently the prevailing class, the lamellibranchs fewer and 

 the cephalopods almost wholly absent. On the outer edge of the reef 

 where the surf beats with wild force and the corals best flourish there are 

 the thick shelled mollusks which without hiding defy the surf ; species of 

 Conus, Ricinula, Fasciolaria, Turbinella and Trochus. The ponderous 

 Monomerellas, Rhinoboli, Trimerellas, Pentamerus, Megalomus, Goni- 

 ophora crassa and the numerous large gastropods were obviously 

 adapted to similar life conditions on the Guelph reefs, and the contrasting 

 abundant small gastropods, brachiopods and lamellibranchs found congenial 

 conditions in the cavities between the branches of the coral stocks and in 

 the ponds among the alga patches on the reef. 



More than one consideration suggests that increasing salinity assisted 

 the development of the thick shelled mollusks. We must look upon the 

 Guelph as a distinct phase in the development of the vast Niagaran coral 

 sea into the desiccating, inclosed sea of the Salina stage, when the salinity 

 of the water finally destroyed all life. The subsequent discussion of the 

 Guelph will show that the Guelph sea was the outcome of a shrinking of 

 the Niagaran sea; it is a derivative of the Niagaran fauna, specially of that 

 element which distinguishes the Racine dolomite of Wisconsin, but it has 

 greatly diminished and its residuum shows a definite adaptation to peculiar 

 conditions. It is therefore legitimate to conclude that the inclosure and 

 desiccation of the continental Niagaran sea had already begun to manifest 

 its influence. Investigations of recent marine faunas sufficiently support 

 this view. Von Baer has shown ' that in the deep eastern channel of the 

 Caspian sea the magnesian carbonate is much increased and the calcium 

 salts are decreased over their relative proportions elsewhere ; under this 

 altered composition of the sea water the shells grow thick and heavier, 



1 Neues Jahrb. fur Mineral. 1856. p. 591. 



