154 L. HELLIS-COLINVAUX 



of which the first segments are cylmdrical to cuneate and often conspicuously 

 larger than those above although not as large as basal segment; other seg- 

 ments cuneate, with lobed or entire margins, to 4 mm long, 3 mm broad and 

 0-5 mm thick. 



Cortex generally of three series of utricles which are often constricted at 

 their bases; outermost utricles remaining attached after decalcification and 

 appearmg polygonal in surface view, (20-)56-72 (j,m in surface diameter, 

 62-90 [im long ; secondary utricles 47-72 [xm in diameter. 



Nodal medullary filaments remaining unfused, or at times fusing in pairs 

 for a distance of 1-1-5 times the diameter of the filaments. 



Type specimen. Loyalty Islands, vicinity of Luengoni, Lifou, 

 Valet, 1853, 1 October, 1964 (PC; an isotype in Hillis-Colinvaux 

 herbarium). 



Habitat. Growing on coral rock in agitated water at —3m. 



Geographic distribution. South-western Pacific. 



5. Section Grypticae n. sect. 



Halimeda cryptica L. H. Colin vaux and Graham 

 Figures 3, 15, 49. 

 Halimeda cryptica L. H. Colinvaux and Graham (1964), p. 5, Plates 3-5. 



Plants to about 9 cm tall, loosely to somewhat compactly organized, with 

 a small distinct holdfast which is usually less than 1 cm long; calcification 

 heavy to moderate ; colour of lighted and umbral surfaces of plant distinctly 

 different, the lighted surface on drying usually green but sometimes greenish- 

 cream to off"- white, the umbral surface white to cream, both surfaces generally 

 dull though sometimes glossy in younger segments ; branching usually di- or 

 trichotomous ; segments generally plane but occasionally slightly ribbed, 

 brittle, the bases of all but the basal segment attenuated into a short narrow 

 beak or stalk; basal segment usually turbinate, the others most commonly 

 very broadly to depressed ovate or transversely broadly to transversely 

 elliptic, sometimes with upper margins shallowly trilobed and lower margins 

 auriculate to truncate, occasionally and particularly in the lower third of the 

 plant the segments broadly to transversely rhombic or angular-obovate ; 

 segments often largest in the middle third of the plant measuring when dried 

 to 11 mm long, 15 mm broad and about 0-33-0-66 mm tMck. 



Cortex of two to three, less commonly to four series of utricles, with the 

 inner utricles often not particularly expanded at the apices or constricted 

 at their bases ; outermost utricles very broadly obovate to depressed obovate, 

 remaining attached after decalcification or separating slightly, although stUl 



