6i 



contains specimens of all size, and among them is one very large Q (egg-bearing), the carapace 

 of which measures 21 mm. in maximum breadth, the length being 14.5 mm. 



There seem to be two principal colour variations, one being greyish-blue on the carapace 

 and the upper parts of the walking legs, and another in which these parts are chestnut-brown 

 with occasional faint transverse stripes of this colour on the legs. These variations are inde- 

 pendent of age and sex. The chelae of the cT are always white at the outer surface. 



This common species is apparently widely distributed throughout the Indo-Pacific region : 

 it ranges from the Red Sea along the coast of Africa down to the Cape region (Natal), and it 

 occurs in the Indo-Malayan Archipelago, at the Pacific Islands and in the Loo-Choo Archipelago. 

 It is curious, that it seems absent in British India; at least I am not aware of any locality 

 in these reeions. 



"ö 



Cleistostoma de Haan. 



1835. Cleistostoma de Haan (part.). Faun. Japon., Crust. p. 26. 

 1900. Clistostoma Alcock. L. c. p. 372. 



In the convex lateral margins of the carapace and in the operculiform external maxil- 

 lipeds, the merus of which is longer than the ischium (the latter produced at its antero-internal 

 angle) the genus agrees with Paraclcistostoma, but the anterior margin of the front passes with 

 a regular curve into the lateral margins, and the carapace is much convex in both directions. 



Only three species r ) seem to belong to the genus. 



Key to the species : 



1 . Lateral margins of carapace regularly rounded. Exognath oi 



external maxilliped partly visible in outer view. Meropodites 

 of walking legs very broad, flattened at upper surface . . 2 

 Lateral margins of carapace projecting in an obtuse angle at the 

 end of the anterior third of their course. Exognath of external 

 maxilliped entirely concealed in outer view. Meropodites of 

 walking legs slender, not flattened; 2 nd and 3 d pair each with 

 two hairy tubercles on their anterior margin, i st and 4" 1 pair 

 with only one Cl. lingulatum Rathbun ~) 



2. Carapace near lateral margins tomentose, as are also the mero- 



podites of the walking legs; margins of meropodites entire . Cl. dilatatum de Haan 

 Carapace and legs almost naked, meropodites of the latter ser- 



rulate at their anterior, spinulous at their posterior margin . Cl. dotilliforme Alcock 3 ) 



1) Cleistostoma leachi (Audouin) from the Red Sea seems to have, accovding to DE Man, its proper place in Parackistostoma. 

 The latter author refers, though hesitatingly, Cleistostoma tridentatum A. Milne-Edwards to Euplax (see p. 59). 



As to Cleistostoma hirtifes Jacquinot et Lucas (Voy. TAstrolabe" et "la Zélée", t. 6, p. 68, pi. 6, f. 3), it is an obscure species, 

 the genene position of which is doubtful (see also my paper on Macrophthalmus, Zool. Med., v. I, 1915, p. 151, note) and the same 

 may be said of Cleislofsjtoma edwardsi Mac Leay (Smith's 111. Zool. S. Africa, 183S, p. 64). 



2) Proc. Biol. Soc. Washington, v. 22, 1909, p. 108. K. Dansk. Vid. Selsk. Skr., 7. Kaekke, Afd. 5, n» 4, 1910, p. 323, 

 textfig. 7 and 8. Hab. Gulf of Siam. 



3) L.c. p. 373. 111. Zool. "Investigator", Crust., prt 10, 1902, pi. 64, f. I. Hab. Karachi. 



61 



