Hancock's organ explained

Hancock's organ is a lateral concealed sensory organ of gastropods,^[1] a chemo-sensory sense organ found in some sea snails. This organ is found in most of the shelled opisthobranchs.^[2]

A great majority of the bubble shells and sea slugs of the orders Acteonoidea and Cephalaspidea have Hancock’s organs.

Notes and References

1. Hancock, A., (1852). Observations on the Olfactory Apparatus in the Bullidae. The Annals and Magazine of Natural History Vol.IX – Series 2 188-190.
2. Schrödl M. & Neusser T. P. (2010). "Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)". Zoological Journal of the Linnean Society 158: 124-154. .