In some records he is shown as Oris, with one 's'.
In the 1850 US Census for Johnstown, Barry, Michigan the family of Orris Barnum was enumerated as follows:
Household #313; Family #320
Barnum, Orris; 45; M; Farmer; real estate $600; b. VT
Barnum, Electa; 40; F; b. Mass
Barnum, James; 18; M; Farmer; b. NY; attended school during previous year
Barnum, Sophia; 10; F; b. Mich; attended school during previous year
Barnum, Romeo; 3; M; b. Mich; attended school during previous year [sic]