Rhyssoplax olivacea (Spengler, 1797)
Algarve, Gibraltar, Mediterranean, N. Red Sea. On rocks and stones, from shallow water to a few meters deep. Grazer.
Synonyms: estuarii, polii, siculus, striatus, sulcatus
Above and below: 1m deep, under stones, in the harbour, Isola Rossa, NW. Corsica. 17-24mm.
Highly variable in patterns and colours.
The longitudinal sculpture is stronger than that of corallinus.
Chiton squamosus Poli, alias Chiton polii Deshayes, in G. Poli: Testacea utriusque siciliae… vol. IV, Parma 1791.
 
« All the authors confused this species, which is found in Mediterranean only, with Linné’s Chiton squamosus, which is rather different. The figures, given by Poli, of the mediterranean species, are magnified; this magnification, which has not been mentionned, helped in confusing the two species, and we restore them today, by giving the one figured by Poli the name of this famous neapolitan anatomist. » – G. P. Deshayes: “Mollusques” in Bory de Saint-Vincent: Expédition scientifique de Morée, Paris 1833.
Colour sets in specimens from the gulf of Cagliari, S. Sardinia.
Original pictures provided by A. Nappo (IT).
(CC BY-NC-SA) –
Intermediate valve of a specimen. Width circa 5,5mm.
Notice the two anterior projections of the white underside; these “sutural laminae” belong to the “articulamentum”, which links the plate to its anterior neighbour.
The species is more strongly carinated than corallinus.
The underside shows two generic features: S - each of the lateral protrusions, called “insertion plates”, bear a single slit; these plates, which are not very developed in this species, hang the valve to the mantle. JS – The jugal sinus, between the two sutural laminae, is denticulate.
Detail of the jugal area (ridge). The longitudinal folds are sharp. The pattern shows some ocelli inside the blotches.
Detail of the detail.
Notice the pustulose microsculpture.
On rock near a young Haliotis tuberculata lamellosa Lamarck, 1822. Off Acireale, Catania, E. Sicilia. Original picture provided by L. Orselli for iNaturalist – (CC BY-NC).
Under pebble, Ključice creek, southern shore of Tiha Bay, Cavtat, Dubrovnik-Neretva Comitat, S. Croatia.

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