76 THE HABITAT OF THE EURYPTERIDA 



posed the shaft sank through 39 feet of clay and then struck a marl 

 bed one foot thick containing Limnaea, Planorbis, Scrobicularia 

 piperata, Cardium edule, diatoms and Chara. 



Yet another illustration of the nature of the faunas of estuaries 

 may be found in the complete lists given in Verrill and Smith's in- 

 valuable report on the Invertebrate Animals of Vineyard Sound and 

 Adjacent Waters (280). The fauna as there recorded from the sandy 

 shores and bottoms of estuaries of the southern New England coast 

 includes: Insects, Crustacea, Annelids, Gastropods, Pelecypods and 

 Nemerteans all of which, with the exception of the last group, are rep- 

 resented by eight or more species (280, 170, 171); from the bottoms 

 of sheltered estuaries, ponds, and harbors the following fauna is noted 

 as characteristic: 



Insects (4 species), Crustacea (30 sp.), Annelids (13 sp.), 

 Nemerteans (2 sp.), Nematodes (2 sp.), Gastropods (15 sp.), 

 Pelecypods (18 sp.) (Verrill and Smith 280, 176-178.) The study 

 of the brackish water bodies in the region just mentioned has shown 

 that the animal life is very abundant and that the number of species 

 found, while not so great as in the open sea, is still fairly large. Par- 

 ticularly is it to be noted that the species which do occur are abun- 

 dantly represented and are remarkable for their hardiness and ability 

 to live under widely varying conditions. A few of the species are 

 restricted to the brackish water, but by far the largest number are 

 able to live in pure sea water. 



SUMMARY OF FAUNAE CRITERIA FOR DETERMINING THE TYPE OF AN 

 AQUEOUS HABITAT 



The chief f aunal characteristics of recent aquatic bionomic realms 

 may now be summarized. 



1. The typical marine fauna is widespread, large, with an abun- 

 dant representation in individuals, species, and genera from practical- 

 ly all of the phyla of the invertebrate animal kingdom. The various 

 lithologic facies have their peculiar faunules, but each one of these 

 contains types from all or nearly all of the phyla, while many cos- 

 mopolitan species, particularly among the pelagic plankton and nek- 

 ton are entirely uninfluenced by the substratum and their remains 

 consequently will be found with those of forms restricted to particu- 

 lar facies. Furthermore, terrestrial and fluviatile organisms will quite 

 frequently be found in the marine fauna, having been transported 



