Not sure if octopus (1st choice) or squid (large eye?).
I thought this was a rams horn but can not find that so will start with gastropods.
Washed up on the Tohe.
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural κεφαλόποδα (kephalópoda); "head-feet"). These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishermen sometimes call them inkfish, referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.