The headword is nominative plural -- presumably quoted from somewhere -- of the noun sh/y (which is related to the verb sh/pw "putrify": sigma 350, and cf. sigma 330). Same entry in ps.-Zonaras and (according to Adler) a similar one in the Ambrosian Lexicon; Hesychius has the same headword but glosses it 'creeping creatures, snakes'.
For the Suda's gloss, see e.g. sigma 338, sigma 684.