segnius : comparative adverb

In this sentence from Orberg LLPSI Cap XLIII: Ab legatis Albanis segnius res acta est it seems that segnius can only be a comparative adverb With the Albani legation the thing moved more slowly. However I can’t see any reference to an advert segnius. L&S gives segniter (adv.) which would seem to bear out my view.

Segnis goes like fortis. Adverb fortiter, comparative adverb fortius, superlative adverb fortissime. So segnissegniter, segnius, segnissime. The comparative adverb goes like the n. acc. comparative of adjectives. (like altior (m,f) altius (n.) from altus (‘‘high’’).

Thanks for this.