posed the shaft sank through 39 feet of clay and then struck a marl bed one foot thick containing Limnæa, 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 invaluable 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 represented 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. Particularly is it to be noted that the species which do occur are abundantly 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 FAUNAL CRITERIA FOR DETERMINING THE TYPE OF AN AQUEOUS HABITAT
The chief faunal characteristics of recent aquatic bionomic realms may now be summarized.
1. The typical marine fauna is widespread, large, with an abundant representation in individuals, species, and genera from practically 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 cosmopolitan species, particularly among the pelagic plankton and nekton are entirely uninfluenced by the substratum and their remains consequently will be found with those of forms restricted to particular facies. Furthermore, terrestrial and fiuviatile organisms will quite frequently be found in the marine fauna, having been transported
