At the time of her marriage to Dyer, she was called "of Royalstown [Roualsborough]." -- [Genealogy of Edward Small (The Dyer Family)]
Calvin Cowing married again in 1819, so perhaps Tamma had died?
Sources
"Massachusetts, Births and Christenings, 1639-1915," index, FamilySearch (https://familysearch.org/ark:/61903/1:1:FZZR-7H4 : accessed 12 May 2015), Thomasine Dennison, 15 Mar 1758; citing GLOUCESTER,ESSEX,MASSACHUSETTS, ; FHL microfilm 0823641 V. 1-2.
"Maine, Births and Christenings, 1739-1900," index, FamilySearch (https://familysearch.org/ark:/61903/1:1:F49Q-XVX : accessed 14 May 2015), Tamisin Dennison in entry for Jene Dyer, 25 Jan 1780; citing Durham, Androscoggin, Maine; FHL microfilm 10,821.
"Maine, Deaths and Burials, 1841-1910," index, FamilySearch (https://familysearch.org/ark:/61903/1:1:F486-B8C : accessed 14 May 2015), Tamisin Dennison in entry for Jene Dyer, 18 Nov 1780; citing reference p59; FHL microfilm 10,821.
"Maine Vital Records, 1670-1907 ," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:2HJB-Y8W : accessed 10 August 2015), Femison Dennison in entry for William Dyer, 04 Jul 1782, Birth; citing Durham, , Maine, United States, State Board of Health, Augusta; FHL microfilm 1,002,332.
"Maine Births and Christenings, 1739-1900," , FamilySearch (https://familysearch.org/ark:/61903/1:1:F49Q-XJT : accessed 10 August 2015), Tamisin Dennison in entry for William Dyer, 11 Jul 1782; citing Durham, Androscoggin, Maine; FHL microfilm 10,821.
"Maine, Births and Christenings, 1739-1900," index, FamilySearch (https://familysearch.org/ark:/61903/1:1:F49Q-6Y1 : accessed 12 May 2015), Tamisin Dennison in entry for Benjamin Broad Street Dyer, 25 Jan 1784; citing Durham, Androscoggin, Maine; FHL microfilm 10,821.
Descendants of Edward Small of New England, Vol. 1: Author: Underhill, Lora Altine Woodbury: Publication: Houghton Mifflin Co., Boston & New York, 1934: Note: NS113603: Source Media Type: Book: Master Listing Source: Y
Family Tree Maker CD523: Title: Maine Historical & Genealogical Recorder, Vol. III, 1886: Publication: Maine & New Hampshire Settlers, 1600's-1900's (CD523): Note: NS195373: Source Media Type: Book: Master Listing Source: Y
History of Durham, Maine: Author: Stackpole, Everett S.: Publication: Somersworth, Strafford, Nh, New England Press, 1899, 1979: Note: Source Media Type: Book: Master Listing Source: Y
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