4 FAUNA OF NEW ENGLAND. 



tant factors governing distribution and the area should be large 

 enough to enable one to study the effects of these varied conditions 

 to advantage. To appreciate fully the true gulf or land-locked 

 character of the Gulf of Maine, one should study a chart covering 

 the Gulf, adjacent coast lines, and banks. This shows at once the 

 desirability of adopting the 200-fathoni line, as any less depth 

 would give a very irregular and impracticable boundary, there 

 being several places in the Gulf of Maine deep>er than 150 fathoms 

 but not exceeding 200 fathoms, while all of the Georges Bank is 

 less than 50 fathoms. The most convenient eastern boundary 

 therefore would be the 66th meridian which just grazes the eastern 

 edge of the Georges and includes the approach to the Bay of Fundy, 

 the tides of which have such a great influence on the fauna of the 

 Maine coast. On the eastern edge of the Georges at about 40° 30' 

 north latitude the 66th meridian intersects the 200-fathom line, 

 which practically skirts the edge of the continental shelf to a point 

 directly south of Montauk Point, Long Island, — about 40° north 

 latitude and 72° west longitude. This gives an area south of the 

 Georges and Cape Cod, si;flici(^nt for the study of the influences of 

 the Gulf Stream and counter currents. All of Long Island Sound 

 except the bays and harbors of Long Island is also included in this 

 area. 



The land mollusks also present many interesting features in dis- 

 tribution, since New England is the northeastern limit of distribu- 

 tion of many species, such as Polygyra palliata, Polygyra tridentata, 

 Omphalina fuliginosa, Omjjhalina inornata, etc., species common 

 to the mountains of North Carolina and Tennessee. We can trace 

 these species back and find that their line of dispersal from that 

 region was probably first northward along the western ridges of the 

 Alleghanies into central New York and thence eastward along the 

 valleys of the Mohawk and Hudson Rivers into western New 

 England. The distribution of Helix hortensis, confined to the 

 islands and headlands of the coast, strengtliens the theory of 

 botanists and others of a large continuous land area to the eastward 

 in comparatively recent geological times. 



Of the species from deep water, only those actually taken within 



