l^l*^] FROM MERGUI ARCIUPELAQO. 807 



in the proportions of tlie European iuul the Indo-Pacific forms, 

 that I retain for the latter a distinct \arietal name. 



Locality. St. 29, reef off High Peaked Island, shore. 



Although P. cavolinii in its varying forms has been recorded 

 from Eastern Australia (Hale, 1884. 1893 ; Lendenfeld, 188.5), 

 and from the East Indies (Pictet, 1893; Campenhausen, 1890; 

 Weltner, 1900), the only records for the Indian Ocean are those 

 of Warren (190(>, 1907, and 1908, as Ihdoconlyle coojnri, .syn. 

 Feyinaria australis. var. cooperi) and that from Christmas Island 

 in the paper following. 



II. CALYPTOBLASTEA. 

 Family H a l e c I D .«. 



Haleciu.m SIMPLE.X Pictet, 1893. (Plate LXXVII. figs. 10 &. 

 11.) 



This verj- rare species is represented by closely woven colonies 

 covering the surface of a Polyzoon which is clustered at the base 

 of colonies of Corydendrium sessile. The presence of the gono- 

 some, so far uudesci-ibed, renders these specimens of particular 

 interest. 



Trophosome. — To the naked eye the minute colonies are 

 almost invisible, the hydranths being most easily di.scerned as 

 they project from the surface on which the colonies grow, 

 in close groups, resembling clusters of the smaller species of the 

 entoproctan polyzoon, Pedicellina. 



The stolon strands are of small diameter, but can often be 

 traced foi' a considerable distance. Their courses are com- 

 plicated, however, by the occurrence of offshoots, which, uniting 

 with other stolons, form a network which lies closely upon the 

 substratum, or is interwoven with it. 



Short, unbranched, unwrinkled hydrocauli arise from the stolon 

 at short distances from each other. Bnsally their diameter is 

 small, but it gradually increases until, at the ba.se of the hj-dro- 

 theca, the girth of the hydrocaulus is about equal to that of the 

 stolon. The hydrotheca; are very small. Their walls, which are 

 well developed, form an inward curve to the margin, so that, 

 instead of being flaring or trumpet-shaped, as in many species of 

 JIalecium, they are rather saucer-shaped. Very clo.se to the 

 margin occurs a ring of bright dots, chitinous prominences on 

 the inner surface of the hydrotheca to which the hydrant h was 

 attached. Here the internal ])rominence.s are more liighiy lieve- 

 lopcd than in any other species I have examined, for they .sometimes 

 rise into pronounced spines 7 /it in length (PI. LXXVII. fig. 11). 

 Occasionally two or even three hydrothecac occur in succes,sion, a. 

 new hydrocaulus arising from within an old hydrotheca. 



The hydranth is of g:-eat size. When contracted it is about 

 twice as long as the hydrooaidus, but when extended it reaches a 

 length of one millimetre or even more. It con.•^ists of a long 



[9] 



