1910.] FROM MERGDI ARCHIPELAGO. 821 



Localities. St. 1, east of Tavoy Island and Port Owen, 4 to 12 

 fathoms, sand and broken shells, and mud; common. St. 14. 

 Bush by Island jjearliug-gi-ound, shore to 21 fathoms, sand and 

 mud; common. Stt. 15 and 16, Ravenshaw Island, Sir John 

 Malcolm Island, and Alligator Rock, 5 to 18 fathoms, rock and 

 .sand, or rock and mud ; common. St. 22, Hastings Harbour, 

 shore to 20 fathoms, rock and sand ; common, with gonano-ia, 

 some colonies growing on a sponge. St. 23, Five Islands, 8 to 

 12 fathoms, rock and sand, and mud; fairly common. St. 25, 

 Gregory "Group and Crichton Island, 4 to 14 fathoms, stones and 

 broken shells and rock ; common. St. 35, between Warden 

 Island, Howe Island, and Lyall Island, 15 to 20 fathoms, rock 

 and sand ; one colony. Moskos Islands, 3 to 2G fathoms, rock 

 and sand, or rock and mud ; common, with gonangia. 



DiPHASIA DIGITALIS Busk, 1852. 



In these specimens it is clearly seen that the two so-called 

 opercular muscles are attached, not to the valves of the operculum, 

 but to the lateral walls of the hydrotheca near the margin, and 

 are, in function, protractor muscles (see Nutting, 1904, p. 13, 

 fig. 17). The hydranth possesses about twenty tentacles. 



Locality. St. 1, east of Tavoy Island and Port Owen, 4 to 12 

 fathoms, sand and broken shells, and mud ; several small colonies, 

 on the bare axis of an Alcyonarian, and on Idia pristis. 



Recorded from the Western Indian Ocean — Maldive Islands— 

 by Borradaile (1905, p. 842) ; this is the first record from the 

 Eastern Indian Ocean. 



Sertularia turbinata Lamouroux, 1816. 



{=S. loculosa Busk 1852 *.) 



Several small, unbranched colonies of this species occur upon 

 Thyroscyphus vitiensis. They are pale in colour, in this, as well 

 as in the shortness of the internodes, agreeing with the specimens 

 described from Paumben, India, by Jiiderholm (1903). But they 

 difl'er in the reduction of the lateral teeth, which are occflsionally 

 so indistinct that the aperture appears to be almost round. 

 Besides an indistinct tooth on each ilank, tlie hydrotheca is 

 surmounted by a small third tooth, from the summit of which a 

 membranaceous edge sometimes runs to the lateral teeth. Not- 

 withstanding difficulties of observation, I feel assured, after 

 examining many hydrotheca', that the operculum is formed of a 

 solitary flap, hinged on the distal edge of a sliglit thickening 

 which occui-s on the abcauline margin of the hydrotheca. 

 Although membranes unite the superior with the lateral teeth, 

 these do not hinge inwards, and can .scarcely, therefore, be 

 accounted part of the operculum. They are the less nccc.s.sary 

 since the abcauline flap is of diameter sufficient comi)letely to 

 close the aperture of the hydrotheca. 



• Fide BillarJ (1909, p. 322), who Las ciaiuincd llic Ivpe specimen of Laniouroui. 



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