1910.] FROM MERGUI ARCHIPELAGO. 807 



in the proportions of the European aiid the Indo-Pacilic forms, 

 that I retain for the latter a di.stinct varietal name. 



LoGcdily. St. 29, reef oft" High Peaked Island, shore. 



Although F. cavolinii in its varying forms has been recorded 

 from Eastern Australia (Bale, 1884, 1893; Lendenfeid, 1885), 

 ;uid from the East Indies (Pictet, 1893; Campenhausen, 1896; 

 Weltnei-, 1900), the only records for the Indian Ocean are those 

 of Warren (1906, 1907, and 1908, as Halocordyle cooperi, syn. 

 Pennaria australis, var. cooperi) and that from Christmas Island 

 in the paper following. 



II. CALYPTOBLASTEA. 



Family Halecid^. 

 Halecium simplex Pictet, 1893. (Plate LXXVII. figs. 10 & 



This A^ei-y rare species is represented by closely Avoven colonies 

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

 of colonies of Cori/dendrium sessile. The presence of the gono- 

 some, so far undescribed, renders these specimens of particvdar 

 interest. 



Trophosome. — To the naked eye the minute colonies are 

 almost invisible, the hydranths being most easily discerned as 

 they project from the surface on which the colonies groAV, 

 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 for a considei'able distance. Their courses are com- 

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

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

 substi-atum, or is interwoven with it. 



Short, unbranched, unwrinkled hydrocauli arise from the stolon 

 at short distances from each other. Basally their diameter is 

 small, but it giadually increases until, at the base of the hydro- 

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

 stolon. The hydrothecse are very small. Their walls, which are 

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

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

 Halecittm, they are rather saucer-shaped. Very close to the 

 margin occurs a i^ing of bi-ight dots, chitinous prominences on 

 the inner surface of the hydrotheca to which the hydranth was 

 attached. Here the internal prominences are more highly deve- 

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

 rise into pi'onounced spines 7 jj, in length (PI. LXXVII. fig. 11). 

 Occasionally two or even three hydrothecse occur in succession, a. 

 new hydrocaulus arising from within an old hydrotheca. 



The hydranth is of great size. When contracted it is about 

 twice as long as tlie hydrocaulus, but when extended it I'eaches a 

 length of one millimetre or even more. It consists of a long 



