I gave up several times before I eventually found the answer on FamilySearch.org.
FamilySearch.org yielded birth record and death record extracts for Sydner D. Richards (d. 1883), the son of George Richards and Mary Commons Richards.
Of course it says Sydner! Amazing how easy a gravestone is to read when you already know what it says.
G.[H.] & M.A.
Aug. 20, 1883
6 [Ms. &] 6 Ds.
The short epitaph, barely legible, is from Luke 18:16, Suffer little children to come to me.
I suspect a transcription error with the birth record. The death record indicates he was born in 1883, as does his gravestone. Aged 6 [Ms.]
Union Cemetery, Franklin County, Ohio