Meaning of phrase

The boy gave him a look of such malice that Mr Bose bit the end of his moustache and fell silent, shuffling through the pages. 'Read on, then' he mumbled and listened, for a while, as Pritam, the boy, blundered heavily through the Sanskrit verses that rolled off his father's (a Brahmin priest) experienced tongue, and even Mr Bose's shy one, with such rich felicity.

What does the parts in bold mean?

Thanks in advance.