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(Bate, 1888)

Diagnosis:
Carapace with three distinct acute teeth in the median line before the cervical groove (the gastric, pregastric and rostral teeth). Region between the postrostral and branchial carinae with only few tubercles and with extensive smooth areas. Abdomen without a sharp elevated median longitudinal carina, but each of abdominal somites 2 to 5 with an elongate lobulate figure in the middle. The exposed part of abdominal somites 2 to 5 with an arborescent arrangement of very narrow grooves. Somite 1 with a complete transverse groove, behind which there are numerous short longitudinal grooves that may be rather irregular in shape and sometimes are interconnected by transverse grooves; this posterior part of somite 1 is longer in the middle than laterally. The smooth anterior half of abdominal somites 2 to 6 (i.e, the part that disappears under the tergum of the previous somite when the abdomen is fully stretched) on either side with a short transverse groove in which hairs are implanted. Fourth segment of antenna with a single oblique median carina. Outer margin of the segment with 2, the inner margin with 3 or 4 teeth (not including the apical tooth). Thoracic sternum anteriorly U-shapedly incised in the middle. A blunt and low but conical tubercle on the last thoracic sternite. Dactyli of legs without fringes of hair.
Colour: pale brownish or pinkish with patches of darker hairs. Two dark spots on the dorsal surface of the first abdominal somite in the submedian region.

Type:
Type locality of Arctus pygmaeus: " off Gomera, one of the Canary Islands, ... lat. 28°N., long. 16°5'W: depth 78 fathoms [= 143 m]; bottom, volcanic sand". Ovigerous female holotype in BM.
Type locality of Arctus immaturus: "dredged off Cape Verde [Sénégal], but neither station nor depth are recorded". Lectotype in BM.

Diagnostic Features:
Carapace with three distinct acute teeth in the median line before the cervical groove (the gastric, pregastric and rostral teeth). Region between the postrostral and branchial carinae with only few tubercles and with extensive smooth areas. Abdomen without a sharp elevated median longitudinal carina, but each of abdominal somites 2 to 5 with an elongate lobulate figure in the middle. The exposed part of abdominal somites 2 to 5 with an arborescent arrangement of very narrow grooves. Somite 1 with a complete transverse groove, behind which there are numerous short longitudinal grooves that may be rather irregular in shape and sometimes are interconnected by transverse grooves; this posterior part of somite 1 is longer in the middle than laterally. The smooth anterior half of abdominal somites 2 to 6 (i.e, the part that disappears under the tergum of the previous somite when the abdomen is fully stretched) on either side with a short transverse groove in which hairs are implanted. Fourth segment of antenna with a single oblique median carina. Outer margin of the segment with 2, the inner margin with 3 or 4 teeth (not including the apical tooth). Thoracic sternum anteriorly U-shapedly incised in the middle. A blunt and low but conical tubercle on the last thoracic sternite. Dactyli of legs without fringes of hair. Colour: pale brownish or pinkish with patches of darker hairs. Two dark spots on the dorsal surface of the first abdominal somite in the submedian region.

Geographical Distribution:
The entire Mediterranean (but not yet reported from the North African coast east of Morocco), and Atlantic islands (Madeira, Canary Islands, Cape Verde Islands).

Habitat and Biology:
Depth range from 5 to 100 m. Ovigerous females in June and August.

Size:
Maximum total length 5.5 cm, usually not more than 4 cm. Carapace length to 1 cm (males) and 1.15 cm (females).

Interest to Fisheries:
Probably nil. The report in Fiches FAO d'Identification, Méditerranée et Mer Noire, vol. 1: 319, that the species is fished for in Sardinia with trammel nets and lobster pots and is regularly present at the markets, where it is sold fresh, needs to be considered with much reserve. It is possible that this information is based, not on S. pygmaeus, but on S. arctus.
The small size of S. pygmaeus does not make it an attractive fisheries object. In N.E. Spain, the fishermen, when they got S. pygmaeus in their nets, threw it back in the sea, in the conviction that these were juvenile Scyllarus arctus, which needed still some time to grow up to acceptable size.

Pygmy locust lobster (Scyllarus pygmaeus)