P. marmoratus has a square carapace 22–36 millimetres (0.87–1.42 in) long, which is dark violet brown with marbling in yellow.
It can be distinguished from related species of Pachygrapsus in the Mediterranean Sea (Pachygrapsus maurus and Pachygrapsus transversus) by the presence of three teeth on each side of the carapace.
It is capable of very rapid movements, and it uses this ability to dart into crevices, making it difficult to catch.
P. marmoratus has a square carapace 22–36 millimetres (0.87–1.42 in) long, which is dark violet brown with marbling in yellow. It can be distinguished from related species of Pachygrapsus in the Mediterranean Sea (Pachygrapsus maurus and Pachygrapsus transversus) by the presence of three teeth on each side of the carapace. It is capable of very rapid movements, and it uses this ability to dart into crevices, making it difficult to catch.
Pachygrapsus marmoratus