Petrolisthes lamarckii (Leach, 1820)

(Fig. 2C)

Pisidia lamarckii Leach, 1820: 54 [type locality: not specified]

Porcellana dentata H. Milne Edwards, 1837: 251 [type locality: Java]

Porcellana pulchripes White, 1847: 129 [nomen nudum]

Porcellana speciosa Dana, 1852: 417 [type localities: Drummond Island, Kingsmills Group; Wake Island; Mangsi Islands, Philippines; Raraka, Tuamotu Archipelago]

Porcellana bellis Heller, 1865: 76 [type locality: Nicobar]

Petrolisthes dentatus – Calman, 1909: 706

Petrolisthes lamarckii – Orchard, 2012: 57

Material examined. Christmas Island: stn CI-31, Ethel

base rock, 2 February 2010, 1 male (cl 10.7 mm), 2 females (cl 4.6, 11.4 mm), 1 ovigerous female (cl 9.5 mm), ZRC 2013.0839; stn CI-09-2011, Ethel Beach, 10°27.805’S, 105°42.443’E, intertidal, limestone base rock, 21 March 2011, 1 ovigerous female (cl 10.2 mm), ZRC 2013.0840.

Colour in life. Based on an ovigerous female (cl 10.2 mm, ZRC 2013.0840) from stn CI-09-2011. Carapace greenish brown, with irregular-shaped dark brown blotches symmetrically arranged and with numerous white spots. Abdomen brown, with irregular transverse line of reddish brown blotches on each segment and covered with white spots. Ocular peduncles greenish brown. Third maxillipeds greenish brown dark greenish brown; dactylus and ventral margin of propodus orange. Chelipeds greenish brown with irregular dark brown blotches on dorsal surface; tips of fingers and proximal end of cutting edge of dactylus pinkish orange. Ambulatory legs generally greenish brown with numerous white spots on lateral surface; merus and carpus with irregular dark brown blotches; propodus dark reddish brown, with white bands proximally and distally; dactylus red, with proximal white patch.

Distribution. Throughout the tropical Indo-West Pacific, Sea, eastward

259 Osawa: Porcellanidae from Christmas and Cocos (Keeling) Islands

to Line and Tuamotu Islands; intertidal, found under rocks (Osawa & Chan, 2010).

Remarks. Calman (1909) listed Petrolisthes dentatus from Christmas Island. Kropp (1984) mentioned that a photograph of the type of Porcellana dentata shows four fairly welldeveloped teeth on the dorso-anterior margin of the carpus of the cheliped which the late Janet Haig informed him is suggestive of Petrolisthes haswelli. Nevertheless, as noted by Osawa & Chan (2010), this feature can be present in P. lamarckii.

The present specimens all were collected from Ethel Beach, and have the following characters: the rostrum is weakly trilobate; a pair of the epigastric spines are small or welldeveloped; the carpus of each cheliped is armed with four or five teeth on the dorso-anterior margin, the distal-most tooth is occasionally obsolete. The female (cl 11.4 mm, ZRC 2013.0839) from stn CI-31 differs from the other specimens examined in the colouration of the chela and the armature of the second pereopod (first ambulatory leg). The chela of the female has a row of orange spots along the anterior margin, but such a row of spots is absent in the other specimens. The merus of the second pereopod of the female is armed with a more strongly developed spine at the ventrolateral distal end than that of the other specimens, and the carpus bears a small dorsodistal spine which is absent in the others. These characters of the single female agree with those of one of two forms of P. lamarckii reported by Osawa & Chan (2010: figs. 109–111, 113d–f).

As mentioned above, the colouration in life was recorded only for an ovigerous female (cl 10.2 mm, ZRC 2013.0840) from stn CI-09-2011. The overall colour is brighter and the dark brown blotches on the carapace are larger than those reported by Osawa & Chan (2010: figs. 109–111).