The mouth of the Cachalot is armed with teeth of ivory, finely set, for the purpose of prehension, and the animal is endowed with the power of descending to the remote caverns of the ocean in search of its prey, and remaining there a length of time unequaled by any of its congeners. The principal food of the Sperm Whale is familiarly named by the whalers “squid ;” which includes one or more species of cuttle-fishes (cephalopods). The animal’s manner of pursuing its prey is not definitely known ; but several high authorities maintain, that after descending to the desired depth it drops its lower jaw nearly to a right angle with the body, thereby exhibiting its polished white teeth, which attract within its reach the swimming food, while the creature moves along through the ocean’s depths ; the moment its prey comes in contact with the expanded jaw. it is instantly crushed, and a portion or all is swallowed. This hypothesis of the mode in which the animal feeds may be correct. As to the nature of its food there is no question, for it is well known that the cephalopods are its main dependence; yet occasionally the codfish, albicoro, and bonito, are laid under contribution. But the true and natural way in which this great rover of the hidden depths seeks and devours its animal food, is still tinged with mystery. — Scammon 1874
Almost a century and a half later, and the “true and natural way” in which sperm whales seek out and dispatch some of the largest and most elusive animals on the planet is still very much “tinged with mystery.” So far as I know the “teeth as lures” hypothesis has pretty much fallen out of favor. I wonder if the "giant eyes of squid are better to see the bioluminescent bow-waves of hungry whales" hypothesis will prove any more durable.
Anyway I love this overdarkened scanned version of this lithograph, itself tinged with mystery. But the better version borrowed from BibliOdyssey does a better job showing what Scammon was talking about.