These are “Phillobothrium delphini”
What is interesting concerning these parasites is that cestodes, like most animals, are named for their adult form (the tape worm) which has never been described, or more likely is well know, but not related to their other earlier life stages. This means that the two parasites Phyllobothrium delphini and Monorygma grimaldii are incorrectly named. It is historically common for a single species of a parasite to be given different formal scientific names for each life stage, but this is clearly an error. DNA analysis may shed light on this issue, and it appears that they both belong to the same genus which is likely Clistobothrium (Agusti, Aznar et al. 2005). Formal proof and renaming of these parasites, which are well known to anyone who does a lot of cetacean necropsies, has not happened yet, but hopefully the issue can be resolved in the near future. The cetacean is an intermediate host for this parasite and the adults are presumed to be large pelagic sharks that would either prey on or scavenge on cetaceans.
Agusti, C., F. J. Aznar, et al. (2005). “Morphological and molecular characterization of tetraphyllidean merocercoids (Platyhelminthes: Cestoda) of striped dolphins (Stenella coeruleoalba) from the Western Mediterranean.” Parasitology 130(Pt 4): 461-474.
Meanwhile this parasites can still be identified by one of the common shapes, host and location
I give you “Phyllobothrium deliphi”