106 L. HILLIS-COLrNVATJX 



suprabasal segment fan-shaped, at times small, but also to 12 mm long, 

 20 mm broad, bearing a few to eight or more branching series of segments 

 which tend to lie flat; other segments to about 12 cm long, 16 cm broad, 

 ovate to reniform, their bases often a little contracted, the distal margins 

 entire to frequently slightly three to seven crenate, to 12 mm long, 17 mm 

 broad. 



Cortex of three or more series of utricles ; outermost utricles remaining 

 attached after decalcification often by a very thin extension of the utricle, 

 or separating slightly, 22-69 fjim in surface diameter, two or four supported 

 by each secondary utricle; secondary utricles of approximately the same 

 diameter as the peripheral utricles, and two to seven times as long. 



Nodal medullary filaments uniting as a single group for a distance about 

 equal to the filament width, adjacent filaments communicating by pores; 

 walls in the region thickened and pigmented. 



Type specimen. North Borneo, Pulau Gaya off the east coast, 

 Cleland, Station 10, 5 February, 1965 (MICH). 



Habitat. Grows on unconsolidated substrates, in shallow water. 

 The extent of its vertical range is, at present, not known. 



Geographic distribution. South-western Pacific. 



The Rhipsalian Halimeda this species most closely resembles is 

 simulans. Although few samples of borneensis are presently available for 

 an extensive evaluation of characters, the following comparisons can be 

 made. The basal or suprabasal segment in borneensis is generally 

 conspicuously broad, and the other segments often both broader and 

 more reniform than those of simulans. The general appearance of 

 borneensis is of a somewhat squatter, more heavy-set plant. 



Microscopic differences include the peripheral utricles being some- 

 what larger and less firmly joined laterally in borneensis as compared to 

 simulans. In addition, the secondary utricles of borneensis are generally 

 longer, sometimes considerably more so, than those of simulans. 



Halimeda borneensis is not known from the Atlantic where simulans 

 is common, but there may be some overlap of ranges in the Indo- 

 Pacific. 



At times the species borneensis and macroloba could be confused, at 

 least initially, and more data are needed on geographic and reef 

 distribution to know the extent of overlap in their ranges. Differences 

 between these two species are discussed under macroloba. 



Both the habitat and habit of borneensis are distinctly different from 

 those of micronesica, a species to which Taylor (1975) compared it, 

 although there is a similarity in the especially large basal or suprabasal 

 fan-shaped segments of the two. 



