I've been studyig this new information. Young A. Purcell's wife and children were all buried in the Arrow Rock Cemetery, as was his sister-in-law, Sarah Prudence Dickson, and other Dicksons. The cemetery cross references names with burial plot numbers, which makes for interesting analysis.
The Dicksons and the related Purcells were all buried together, right next to each other (except for the two who lived to be ancient--they are buried directly adjacent to the rest, but one row over). So the ones who died young are there, as are their siblings who died almost a hundred years later. All together.
Young Purcell's wife's gravestone has a clue--it says "wife of A." so Purcell may have gone by his middle name, Alexander.
The strange thing is, even though the circumstantial evidence tells us Young Alexander Purcell died a few months before his daughter Mary A. Purcell (died 1870--she's buried there too and her headstone says so), he's apparently not there. That circumstantial evidence of his death date is the fact his son Alexander Brooks Purcell was born April 24, 1870, indicative of conception in July 1869. Young Alexander Purcell is gone by the time the census is taken in 1870 and his daughter Mary dies. What's the date the 1870 census pinpointed his family in Saline County? That'll narrow the timeframe down even tighter.
So Young Alexander Purcell dies, his pregnant wife moves to Arrow Rock, where she gives birth to their son Alexander Brook Purcell on April 24, 1870 and buries her daughter Mary A. Purcell around the same time. She herself dies five years later on Oct. 1, 1875, at the age of 37 years and 12 days old, and is buried among the mass of her family.
But what happened to Young Alexander Purcell? His wife Mary Belle apparently buried him and moved to Saline County.
They were pretty well off in 1860. They were still well enough off in the 1870s that everybody else in his family who needed a headstone got a headstone. Surely Y.A. Purcell is somewhere in Missouri and he got a headstone too. Any clues regarding where his father Malcolm Purcell was buried?