@Fujisawas Sake found a poster quoting SOS that lead to a discussion on finding documentation about hard parts being lodged in octopus brains.
Steve remembered this paper.
The gut contents of a female specimen of Graneledone cf. boreopacifica collected from the caldera wall of Axial Volcano, near an active hydrothermal vent in the Northeast Pacific Ocean are reported. At least 30 individual gastropods and 46 individual polychaetes are represented in the gut contents by hard parts. Shell fragments and shells removed from the gut allow ready identification of the gastropods Provanna variabilis and Lepetodrilus fucensis, both of which are known only from North Pacific hydrothermal vents. Jaws of polychaete worms are identified as those of the nereidid, Nereis piscesae, and the predatory polynoids, Levensteiniella kincaidi and an unidentified species in the subfamily Branchinotogluminae. Not only was a considerable volume of prey hard parts ingested, the gastropod shells had been crushed before being ingested. The large size of the beaks in this genus of octopus and the increased area they offer for insertion of the superior mandible muscle, the prime mover in beak closure, support the hypothesis that these beaks exert sufficient force to crush the gastropod shells. Although cephalopods had been reported to be absent from hydrothermal vents, the data presented here demonstrate that not only do they occur in vent habitats, they actively prey on vent fauna.
(Accepted October 26 1999)
The access is subscription only and the portion about the snail shells being embedded in the brain is not in the abstract but Steve added this remembrance from the rest of the article:
"... When preying on gastropods, the octopus crushed shell-bearing snails and ingested them. ... had penetrated the octopus brain (as in other molluscs, the oesophagus goes through the octopus brain). If prey hard parts are routinely ingested by these deep-sea octopuses, the brain ..