Haptophyte
/Today’s drawing was made possible by Plankton Net, “an open access repository for plankton-related information” that has about 15,000 images available to draw from (thus mitigating the artist’s need to use dubious substitutes as models for creatures that are too small to see).
This is a coccolithophore, representing the haptophytes, one of the branches of eukaryotes commonly known as algae.
The original SEM image is Coccolithus pelagicus ssp. braarudii by Richard Lampitt and Jeremy Young (© Jeremy Young, The Natural History Museum, London) https://planktonnet.awi.de/ CC BY 2.5