Two side-by-side, head-to-tail. They were probably in a mating behaviour; nudis are both male and female, and they exchange sperm only which they use to fertilise their own eggs. Now that's true equality of the sexes!
Summary[edit] Description: English: Alder J. & Hancock A. (1845-1855). A monograph of the British nudibranchiate Mollusca: with figures of all the species. The Ray Society, London. Published in 8 parts: Part 1. Fam.1 Plate 4 [1845]. Doris flammea Alder & Hancock, 1844 synonym Doris pseudoargus Rapp, 1827 accepted name. Date: 1845. Source: https://www.biodiversitylibrary.org/item/131598#page/101/mode/1up. Author: Joshua Alder.
Summary[edit] Description: English: photograph of the Warty dorid Doris verrucosa taken on the Atlantic side of the Cape Peninsula off the South African coast in 26m of water, using a Nikonos V camera. Date: February 2009. Source: Own work. Author: Seascapeza.
Summary[edit] Description: English: Found at Star Wall near Hout Bay on the Atlantic Coast of the Cape Peninsula. Length 2cm. Depth 20m. Date:. Source: Own work. Author: AndyT.