Not identified.
It is not known which of the five papers by Castelnau that appeared in the Proceedings of the Linnean Society of New South Wales M's friend requested (for titles see author index to the Proceedings, http://tinyurl.com/yc2m7ss4 viewed 30 December 2017.) The first of these papers was read on 24 September 1877 and the last on 25 November 1878.
Please cite as “FVM-79-04-28,” in Correspondence of Ferdinand von Mueller, edited by R.W. Home, Thomas A. Darragh, A.M. Lucas, Sara Maroske, D.M. Sinkora†, J.H. Voigt† and Monika Wells accessed on