Sentence:  Spring-headed Hydraes, and sea-shouldring Whales, / Great whirlpooles, which all fishes make to flee, / Bright <WSD>Scolopendraes</WSD>, arm'd with siluer scales, / Mighty Monoceroses, with immeasured tayles. 
Meaning of the word marked with <WSD> tags:  A mythical sea-creature, reputed to be able to disgorge its bowels to dislodge any fishing-hook.