EDITED! This text has been edited according to the comment made by @leslieh below.
Bispira cf. mariae
Regarding the difference between B. mariae and B. volutacornis, Trainito and Baldacconi claim in their "Atlante di Flora e Fauna del Mediterraneo" (6th ed. 2021) mariae is the species of the Mediterraneis, whereas volutacornis is found in the Atlantic Sea. But I cannot say how they came by this information.
Sighting the relevant Bispira specimen on iNat I come to the conclusion that the Bispira "volutacornis" respectively "mariae" of the Atlantic coast of Europe are mostly (but not all) comparatively pale in color, variable in color, the bands of the crown are pale or nonexistent. ~ Bispira volutacornis?
The specimen of the Eastern Mediterraneis and Adriatic are mostly (but not all) of a comparatively dark brownish/orange color, mostly with prominent white and black bands. ~ Bispira mariae?
(In the Western Mediterraneis the rate of pale and uniformely colored specimen seems to be somewhat higher than in the E-Med.)
observation is for the blue structure on the edge of the Komplex Padina pavonica. Is it part of the Padina or is it another specimen atop?
left shell: I have read that the mouth opening of Arbacia lixula is much bigger than of Paracentrotus lividus
The five seven photos compare with a similarly sized C. gallina in the Gulf of Lyon (https://www.inaturalist.org/observations/36114509). The specimen considered here is always on the left. In the last two photos (taken > 1 year later) it has become much paler, but it's still the same shell). Last photo highlights the paleal sinus
https://www.biodiversitylibrary.org/item/23343#page/683/mode/1up
http://fishbiosystem.ru/PLEURONECTIFORMES/Cynoglossidae/Symphurus_nigrescens2.html
https://www.semanticscholar.org/paper/Larval-development-of-the-spotfin-tonguefish-and-of-Mart%C3%ADnez-Medina/512df2c04fb55f3362f6bb5c5aa3bcca625f1573#extracted
(Figure 2 of Figures and Tables tab)
Salaria basilisca is a species of combtooth blenny found in the Mediterranean Sea near Tunisia and Turkey, also in the Adriatic Sea. This species reaches a length of 18 centimetres (7.1 in) TL. It is found among seagrass, sometimes where there is a rocky substrate. The male guards the eggs produced by several females. They are protogynous hermaphrodites with individuals being females while young changing to males later.
Made with Olympus TG-5
(source: Wikipedia)
Photo by my diving buddy JI.L.
More close ups to follow if needed, when I get my fins so I can dive easier at the depth where the sponge is located.
Training day of the photo contest.
The photo contest is about the amount of fish. I couldn't resist to photograph also other species. It was in freediving and I never did a course for it. I had a hard time also 5 hours in a row in the water. But a lot of fun!