Tylocarcinus styx

(Herbst, 1803)

Carapace elongate pyriform, regions fairly well defined, the dorsal surface of each region being covered with numerous rounded tubercles, i.e., about 10 on the gastric region, one in the groove separating the gastric and cardiac regions; 3 on the cardiac region, 5 on the intestinal region (one on either side of the posterior border being larger), about 3 on the hepatic region, about 5 on the epibranchial region, about 5 on the mesobranchial region and 2 on the metabranchial region, one of which is elongate and curved, placed on either side of the cardiac region. The pterygostomial and epimeral regions are also finely granulated.
The true rostrum almost obsolete; the pseudorostral spines are slightly deflexed ventrally and fused together in proximal half, the spines being moderately divergent and incurved at tip. The preocular spine extremely prominent, the intercalated spine very small and in close contact with the supraocular eave and the postocular cup. These three orbital components, together with the basal segment of the antenna, form a commencing orbit. The antero-external angle of the basal antennal segment is armed with a prominent spine. The ischium and merus of the external maxillipeds are slender, leaving a wide gap in the median line of the buccal cavern.
Chelipeds are stout in the male, the arm is armed with a few spines on the superior border; the palm smooth, the fingers widely gaping at base, the movable finger being armed with a stout tooth near the base. Merus of the ambulatory legs is armed with a row of two or three spinules along the anterior border, of which the terminal one is very long, and also a row of a few obtuse ones on the upper surface; carpus with a prominent spine near the distal end of the anterior border. Dactylus is strongly incurved, its inner border being armed with 7 or 8 minute teeth.
Abdomen of both sexes seven-segmented. (Sakai, 1938: 271)

Type locality: East Indies.
Range: Red Sea - Elat, Gulf of Suez, and Dahlak Archipelago (Griffin & Tranter, 1974), Abulat (Griffin & Tranter, 1986a); Coëtivy Islands (Rathbun, 1911); Mauritius (H. Milne Edwards, 1834, Bouvier, 1915b, Michel, 1964, Griffin & Tranter, 1986a); Chagos Archipelago - Salomon and Egmont (Rathbun, 1911); Sri Lanka (Alcock, 1895a); Andamans (Alcock, 1895a); Mergui Archipelago (Alcock, 1895a); Japan - Amami-Oshima (Ortmann, 1893), Tosa Okinoshima and Okinawa (Sakai, 1938a), Tosa Bay, Ashizuri-misaki, Yoron, Ishigaki, Taketomi and Iriomote-jima (Sakai, 1976a), Okinawa-jima (Miyake, 1983), Amami-Oshima and Yoron-jima (Muraoka, 1998); Taiwan - Su-ao (Miyake, 1938, Lin, 1949); China - Paracel Island (Chen, 1980), Hainan Island (Dai & Yang, 1991); Palau (Takeda, 1973d); Indonesia - Edam Island, Noordwachter Island and Ambon (de Man, 1887d), Borneo Bank, Banda Sea and Biak, Irian Jaya (Griffin & Tranter, 1986a); Solomon Islands - Florida Group (Griffin & Tranter, 1986a); New Caledonia - (A. Milne Edwards, 1872), Ile des Pins (Takeda & Nunomura, 1976); Fiji (Griffin & Tranter, 1986a); Samoa (Alcock, 1895a); 0-4 m.

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