BUFFALO SOCIETY OF NATURAL SCIENCES 67 



RECENT AQUATIC FAUNAS 



Having established what seem to be fairly accurate limits for the 

 ranges in salinity in all of the waters on the surface of the earth, it 

 becomes possible to study the faunas of these different realms, for the 

 type of life in any given water body is more dependent upon the sa- 

 linity than upon any other physical factor with the exception of ex- 

 tremes of temperature. The absolute necessity of studying recent 

 faunas with particular attention to the types of organisms repre- 

 sented, and to the numbers of species and of individuals, has not been 

 realized sufficiently in the past. The habitats of fossil faunas can- 

 not be determined without a knowledge, an intimate knowledge, of 

 the habitats of recent faunas. To be sure, there is little doubt about 

 the kinds of organisms which make up a typical marine fauna; in 

 many cases, too, there may be no difficulty in recognizing a fresh 

 water (especially lake) fauna, but there is an undoubted haziness and 

 lack of precision in all ideas connected with brackish waters and with 

 the faunas thereof. When a given fossil fauna has shown certain 

 peculiar characteristics, such, for instance, as a complete or almost 

 complete absence of molluscan representatives or when the fauna has 

 been confined to one or two classes of organisms, the custom has been 

 and still is to say that the organisms lived in brackish water. It is, 

 thus, necessary to determine the nature of recent faunas which are 

 characteristic of the various bionomic realms, in order that we may, 

 not without a fair degree of certainty, establish the criteria for de- 

 termining the faunal nature of the habitats of the past. 



Marine. The marine fauna is always large and varied, compris- 

 ing, typically, representatives from each taxonomic division among 

 the invertebrates. Not only are there a large number of genera and 

 species, but nearly all phyla are represented. For the mollusca alone 

 the number of genera in a given region may run up into the hundreds 

 and that of the species may be considerably over a thousand. The 

 figures apply especially to the littoral zone, that belt along all coasts 

 which is most favorable to life. There light penetrates to the bot- 

 tom, the food supply is abundant, and varying substrata are avail- 

 able to suit the needs of different organisms. This zone, extending 

 from high water approximately to the two hundred fathom line, is 

 the one of greatest geologic interest because nearly all of the marine 

 formations of the past were littoral; unequivocal abyssal deposits 

 being very rare. Since practically all of the invertebrate organisms 



