As with other terrestrial arthropod groups such as spiders, scorpions, pseudoscorpions and insects, a variety of species from the four multi-legged arthropod classes (Pauropoda, Symphyla, Diplopoda and Chilopoda), collectively known as myriapods, has been described from seashore sites at different times. However, confusion can occur over both the definition of "littoral" and of the halophilic or otherwise status of particular examples. A term such as "littoral Mediterranean" might refer to shoreline species or to species found in ecosystems along the coast and maybe up to a considerable distance/height above it. Here we use the term to cover species found around high-water mark and below, maybe even down to mid-tide level.

It is often difficult to be clear about the precise status of a species on the shore, i.e. as to whether myriapods found in or close to the littoral zone are obligate halophiles, species that are typically terrestrial but also occur on the shore or just chance occurrences. Filippo Silvestri (1903) referred to:

• "myriapodi halofili genuini" i.e. confined to such habitats (obligate halophiles)
• "myriapodi halofili indifferenti" i.e. occurring in both terrestrial and littoral habitats (facultative halophiles)
• "myriapodi halofili accidentali" i.e. chance occurrences (accidental halophiles)

Such a situation may well be true of all "terrestrial" groups in which some species have invaded the littoral zone. The geophilomorph centipede Hydroschendyla submarina, for instance, has only been recorded from seashores in northern Europe, the Mediterranean and Bermuda and is clearly "genuini", whilst the widespread Pachymerium ferrugineum is clearly "indifferenti" in much of its range. The situation is made more complex by species such as Schendyla peyerimhoffi which appear to be "genuini" in one country but occur inland in another. In many cases, where species are described from a single littoral site, clarity of status is impossible to clarify and these lists may include some species which may later be considered "accidentali".

Myriapods have been found in a diversity of sites on the upper shore and around high tide level including under/in strand-line debris, in shingle, under stones on mud and, possibly the most difficult to sample, in rock crevices. Thalassisobates littoralis has been found in pitfall and shingle traps and other species have been extracted from debris using Tulgren (Berlese) funnels.