[Taxacom] abbreviation in Dutch taxonomy paper

[John Grehan]

In a Dutch taxonomic article (1938) there is repeated reference to 'v. d.
M. and I am interested to know what this stands for if anyone is familiar
with this. An example is "Ook een enkele maal te Amsterdam aangetroffen
(Van der Beek, v. d. M.)" which I translate as "Also found a few times in
Amsterdam (Van der Beek, v. d. M.)"

Thanks. John Grehan