Tadpole identification

[Mentat]

...A useful pdf for tadpoles: http://fl.biology.usgs.gov/armi/Guide_to_Tadpoles/SEARMITadpoleGuide.pdf
And the more thorough North American Key: USGS Patuxent Wildlife Research Center "Tadpoles of the United States and Canada: A Tutorial and Key"
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And a list of New England frogs to narrow it down (in case you haven't seen one already) The Frogs of New England: New England Frog Species Information

Colour variations can be tricky in tadpoles, so other clues are usually needed. Like dorsal or lateral eyes. Size of the tadpole. Time of year they were found-> late summer would point to Bullfrog, Green Frog, or Mink Frog. What type of body of water they were found in-> vernal or permanent pond? Scouting the area for adult versions can also be hand (though early spring breeders will often vacate after laying).

Thanks Brian for the information and extremely useful links . Weird how the first PDF was collated with pages in strange sequence; but the info is great!