1910.] fhom mergui archipelago. 817 



hj'postome, and reminding one of the structure of Bomieviella 

 grandis, described bj' Broch (1909 «, p. 195). I have not noticed 

 that in liliss Thornely's species the perisarc is tinged with brown. 

 To Lafoiia venusta I have, with a little doubt, referred my 

 specimens because of the shape, the small size, and the corrugated 

 walls of the hydrothecae. 



Family Sertularid^. 



Sertularella ctlindrica Bale, 1888. Var. p0silla, nov. 

 (Plate LXXVII. fig. 9.) 



Simple stems spring from a creeping stolon, and these are 

 divided into interuodes of exceeding variable length by sUghtly 

 slanting nodes. A.t the distal end of each internode a hydrotheca 

 is borne. 



The hydrothecse are alternate, and have very thin, collapsable 

 walls, in strong contrast with the thick internodal perisarc. In 

 comparison with the stem upon which they are carried, the 

 hydrothecfe are very large. In shape they are cylindrical, the 

 cylinder expanding slightly at the mouth and foi-ming an everted 

 margin, entire, and destitute of operculum. For about a third of 

 their length they are adnate to the internode, but beyond this 

 their free portion curves gracefully away from the stem, so that 

 the aperture faces upwards and outwards, the plane in wliich it 

 lies meeting the stem at an angle of about 45°. A slight break 

 in the even abcauline profile of the bydroiheca opposes the point 

 where the adcauline side becomes free from the stem. Often 

 the bottom of the hydrotheca is rounded. Stolons are occasionally 

 developed from the stems, and one was observed springing from 

 the inside of a hydrotheca. 



Gonosome unknown. 



Dimensions : — 



Var. pusilla. 



Internodes, length 0-27-0-36 mm. 



„ diameter 0"06-0'07 mm. 



Hydrotheca, depth 0-29-0-37 mm. 



„ diameter at mouth 0"10-0'11 mm. 



Typical form.* 

 verj' variable, 

 up to 0'39 mm. 

 0-80-0-84 mm. 

 0-32 mm. 



Localities. St. 32, south-west of Domel Island, 26 to 29 fathoms, 

 sand and mud ; rare, on Lylocarpus phoaniceus. IMoskos Islands, 

 3 to 26 fathoms, rock and sand, or rock and mud ; a single stem 

 amongst the rhizoidal tubes of Idia pristis. 



The species h.-xs hitherto been found only on the east coast of 

 Australia, at Port Jackson (Bale, 1888, p. 765). 



Systematic position. — While I do not find in this form characters 

 sufiicient to separate it specifically from C. cylindrica, it can 

 readily be distinguished from the Austi-alian form, examples of 

 which I have recently had an opportunity of examining, cliiefiy 



* Specimens collected off N»w South Wales by the 'ThetU,' 1808, entrusted to 

 me for examination. 



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