William, thanks for the WikiTree ID. Here's his death certificate:
"Pennsylvania, Philadelphia City Death Certificates, 1803-1915," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:JX3G-GNP : 9 March 2018), James St.Clair Morton, 18 Sep 1880; citing , Philadelphia City Archives and Historical Society of Pennsylvania, Philadelphia; FHL microfilm 2,047,251.
His sister's birth record, same middle name:
"Pennsylvania, Philadelphia City Births, 1860-1906," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:VBTW-MC1 : 10 March 2018), Bertha St. Clair Morton, 16 Oct 1870; citing Birth, Philadelphia, Philadelphia, Pennsylvania, United States, City of Philadelphia, Department of Records, Pennsylvania.
Clearly, his family abbreviated 'Saint.' Also clearly, he was not EuroAristo, so that Project's rules don't apply. I agree with Melanie: Space, no period.