At this position, François Ponsard is mentioned in the Dayot gravure from 1900, though no confirmation exists of his attendance at a vendredi-soirée. Giraud did not caricature him, and Ponsard avoided Paris, preferring to write in his hometown, Vienne (Isère) and Aix-les-Bains. All known images, except one by Lehmann in 1845, depict him beardless, raising doubts about his depiction. If it is Ponsard, he must have shaved after having posed for Biard, or Biard may have used Lehmann’s drawing as a model in absence of Ponsard. Given the initial plan to include actress Rachel Félix in the painting (removed during a redesign in 1854) the presence of her lover Ponsard would be fitting.

Alternatively, this person could be Ponsard’s friend, composer Charles Gounod. He has a better facial fit, and there is proof that he attended several vendredi-soirées. Images from the 1840s and 1850s confirm that he had a well-groomed beard at the time. As with Ponsard, there is no caricature of Gounod by Girard.
Based on the likeness of the images and confirmation of his presence at the Louvre, I would support Gounod for this position, but I recognize the importance of Ponsard, his intimate relation with Rachel, and the fact that his name was added to Dayot’s gravure in 1900.

If I would have had a say in 1855, I would have added them both.