48 1665 (not a very good edition) and the MSS. read 'Mun', which was of course the usual short for Edmund. But 'Mum' in the context is appropriate enough and generally read.
The intense Cambridge flavour of this seems to require special comment by a Cambridge man. For the duties of the 'Prevaricator' refer to Peacock's Observations on the Statutes of the University of Cambridge, 1841 (information kindly furnished by Mr. A. J. Bartholomew).
The Hue and Cry after Sir John Presbyter.
With hair in characters and lugs in text;
With a splay mouth and a nose circumflexed;
With a set ruff of musket-bore that wears
Like cartridges or linen bandoleers
Exhausted of their sulphurous contents
In pulpit fire-works, which that bomball vents;