(Von Siebold, 1824)
Diagnosis:
Anterior margin of narrow cervical incision of the carapace reaching the lateral margin some distance behind the anterolateral angle. Part of the lateral margin of the carapace extends between the anterolateral angle and the cervical incision and bears some teeth there. The carapace bears 10 to 12 (usually 11) posterolateral teeth. Merus of third maxilliped with ventral surface slightly concave, not swollen, and not coloured differently from other segments; inner margin not with deep incisions.
Two subspecies are recognized:
Ibacus ciliatus ciliatus: carapace of adult specimens naked. Lateral margin of carapace with 10 to 12 (Usually 11) posterolateral teeth.
Ibacus ciliatus pubescens: carapace of adult specimen with a thick cover of a velvetly pubescence. Lateral margin of carapace with 11 to 13 (usually 12) posterolateral teeth.
Type:
Type locality of Scyllarus ciliatus: "Japonia", probably near Nagasaki, Kyushu; lectotype in RMNH, no.D 969, in alcohol, condition good.
Type locality of Phyllosoma guerini: "Japonia", probably near Nagasaki, Kyushu; lectotype in RMNH, no. D. 5588, dry condition poor.
Type locality of Ibacu pictus: "en las aguas del Japon"; whereabouts of type material unknown.
Type locality of Phyllosoma utivaebi: "along the shore near our Laboratory" ( = Seto marine biological laboratory, Sirahama, Waka- yama-ken, Japan); 3 syntypes in Seto marine biological laboratory.
Type locality of I. c. pubescens: "Albatross" Station D 5394, near Talajit Island, Philippines, 12°00'30"N, 124°05'36"E"; holotype male in USNM, no.104285.
Geographical Distribution:
Indo-West Pacific region: Japan (south- ward from Niigata on the west coast (ca. 38°N), and from Tokyo Bay on the east coast (ca. 35.5°N)), south coast of Korea to Hainan Island (S. China), South China Sea, Taiwan, east coast of Philippines and Thailand. The subspecies I.c. pubescens has been reported from the Philippines (among the islands and along the west coast), and from Western Australia (W. of Broome).
Habitat and Biology:
Depth range from 49 to 314 m, mostly between 100 and 250 m. The species is found on soft substrates of sand, mud or clay.
Size:
Maximum total length about 23 cm; the carapace lengths reported are 4 to 7.6 cm (males), 4 to 8 cm (females), 6 to 8 cm (ovigerous females).
Interest to Fisheries:
The species is mostly caught by trawlers and sold on the fish markets of Japan, Korea, Taiwan and the Philippines. A report by H. Bürger from about 1830 mentioned that the species could be found every day on the fish markets of Nagasaki and nearby area (Holthuis and Sakai, 1970: 112).