This one is a bit of a puzzle. A number of sources mention three of the graves represented here: Prudent-Villers (far left), medallion of the Mortiers next to Prudent and Jean-Baptiste Clement (far right) but not the name of the grave with the bust of a man. And to make matters worse, the bust in the postcard is presently missing.
However, there is a possible answer to this tiny mystery. In Moiroux's 1908 guide to the cemetery he mentions the grave of French painter and former communard Louis-Ernest Pichio (d. 1898) as being near this very location.
Pichio, also known as "Picq", was perhaps most famous for his painting of the summary execution of 146 communards at this very spot on May 28, 1871.