1910.] FROM MERGUI ARCHIPELAGO. 817 



hypostome, and lemiiiding one of the stx-uctiu'e of Bonneviella 

 grandts, described by Broch (1909 «, p. 195). I have not noticed 

 that in Miss Thornely's species the perisavc is tinged with brown. 

 To Lafoea venusia I have, with a little doubt, i-ef erred my 

 specimens because of the shape, the small size, and the coxn-ugated 

 walls of the hydrothecse. 



Family Sertularii) ,'K, 



Sertularella cylindrica Bale, 1888. Var. pusilla, nov. 

 (Plate LXXVII. fig. 9.) 



Simple stems spring from a creeping stolon, and these are 

 divided into internodes of exceeding variable length by slightly 

 slanting nodes. At the distal end of each internode a hydrotheca 

 is borne. 



The hydi'othec?e are alternate, and have very thin, collapsable 

 walls, in strong contrast with the thick internodal perisai-c. 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 forming 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 a,way from the stem, so that 

 the aperture faces upwai'ds and outwards, the plane in which it 

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

 in the even abcauline profile of the hydrotheca 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 liydrotheca. 



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 O'10-O'll mm. 



Typical f<)rni.» 



very vai'inble. 

 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 Lytocarpus j^hdenice us. Moskos Islands, 

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

 amongst the rhizoidal tubes of Idia pristis. 



The species has hitherto been found only on the east coast of 

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



Si/stematic position. — While I do not find in this form characters 

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

 readily be distinguished from the Australian form, examples of 

 Avhich I have recently had an opportunity of examining, chiefly 



* Specimens collerted nff New .South Wales hy the 'Thetis,' 1898, entrusted to 

 me for examination. 



