Aspidosiphon (Aspidosiphon) muelleri Diesing, 1851  

This species is the most widespread, eurytopic and polymorphic Aspidosiphon, with a long list of synonyms and morphology difficult to define. The anal shield is composed of small units arranged in different sized plates and divided in 3 sections: dorsally the plates are separated by longitudinal furrows, and in the midsection by transverse furrows. Ventrally there are raised wart like or cone shaped units. Specimens may have only compressed unidentate hooks on the introvert, only compressed bidentates or both. The trunk shape varies according to the form of the shelter where the worm is found. However the most common shelter for A. muelleri is discarded gastropod shell.