Shell about 3.5 mm long; found crawling on algae in a low intertidal pool at McKenney Point, Cape Elizabeth.
See:
Ohnheiser & Malaquias (2014. The family Diaphanidae (Gastropoda: Heterobranchia: Cephalaspidea)
in Europe, with a redescription of the enigmatic species Colobocephalus
costellatus M. Sars, 1870. Zootaxa 3774 (6): 501–522.) Available from: https://www.researchgate.net/publication/260684868
https://opistobranquis.info/en/guia/cephalaspidea/cylichnoidea/diaphana-minuta/