Pinacoderm

The pinacoderm is the outer most layer of cells (pinacocytes) surrounding the body of organisms belonging to the phylum Porifera (sponges), equivalent to the epidermis in other organisms.

The pinacocytes (a type of cells) that form pinacoderm are on the external surface of the sponge body and are characterized as an epithelial layer of flattened cells.

It also contains porocytes which are oval shaped cells extended from pinacoderm to choanoderm (layer containing choanocytes). These porocytes line the ostia. Various types of pinacocytes occur—basipinacocytes are in contact with the surface to which the sponge is attached, exopinacocytes are found on the surface of the sponge, and endopinacocytes line the canals. Pinacocytes are flattened cells containing many granules; capable of contracting.

...
Wikipedia