@article{marcus_1956,  title={Notes on Opisthobranchia},  volume={7},  ISSN={0373-5524},  url={https://doi.org/10.1590/S0373-55241956000100002},  DOI={10.1590/S0373-55241956000100002},  number={1-2},  journal={Boletim do Instituto Oceanográfico},  publisher={Instituto Oceanográfico da Universidade de São Paulo},  author={Marcus, Ernesto},  year={1956},  month={Jun},  pages={31–79} }