Sources & Information:
Ancestry.com > Stephen Smith and Lanpheaar Family Tree, Public Member Tree’s, both give date of birh as 1740, Harwich, Barnstable, MA., USA.
Ancestry.com > Cowles-Hennis Heritage, Meisel Family Tree, Publice Member Tree’s, and One World Tree, all give date of birth as 7 Sept 1746, Harwich, Barnstable, MA., USA.
Ancestry.com > OneWorldTree, gives date of marriage for Jabez Gross and Dorothy Ellis as 24 Oct 1763, Wellfleet, MA., USA. See Individual Information below!

Dorothy 'Dolly' Ellis, b. about 1745, baptized 7 Sept 1746, Barnstable Co., Harwich, MA. died. 6 June 1821, Age 76yrs, Interned @ Gross Hill Cemetery located on hill, west of Garrattsville, near Crystal Lake, NY Established about 1812. Edward D. and Kathleen A. Ellis have visited this cemetery in N.Y.

INDIVIDUAL RECORD ---
Dorothy Ellis, female, birth about 1740, Harwich, Barnstable, Ma.
Parents: Father: John Ellis. Mother: Johannah Swift.
Submitter: Harry Hadaway, 10 Timmins Road, Bow, NH 03304.
http://www.familysearch.org/Eng/Search/PRF/individ...f.asp?recid=70705762

INDIVIDUAL RECORD ---
Dorothy Ellis, female, birth 7 Sept 1746, Harwick, Barnstable, Ma. (not they have Harwick not Harwich, Ma.) Parents: Father: John Ellis. Mother: Johanna Swift. (note spelling of Johanna). Source Info: film No. 537430, Pg. No. 22, Ref. No. 32417.
http://www.familysearch.org/Eng/Search/IG...vidual...5230315&ldsnn=12

INDIVIDUAL RECORD ---
Dorthy Ellis (not spelling of Dorothy), female, Christening: 7 Sep 1746, Hardwick, Worcester, Ma. Parents: Father: John Ellis. Mother: Joanna Swift. Source Info: Batch No. 5005597, Source Call No. 1553348, Sheet 4.
http://www.familysearch.org/Eng/Search/IG...vidual...5233470&ldsnn=12

Marker recorded by the D.A.R. in 1937 but not found in 1985.
Gross, ? -wife of Jabez d. Jun 6 1821 age 76 years (stone broken).
Ancestry.com> Stephen Smith, Public Member Tree, Unsourced.
Ancestry.com> Lanphear Family Tree, Public Member TRee, Unsourced.