ECOLOGY AND TAXONOMY OF HuUmeda 127 



A second prominent characteristic of H. cuneata is the extensive 

 attachment of adjacent peripheral utricles which is for approximately 

 0- 3-0-5 of their length. Extensive attachment, however, is not unique 

 for cuneata. The peripheral utricles also adhere for a considerable 

 distance in H. discoidea, and for somewhat shorter distances in H. tuna, 

 and H. incrassata. When working with dried material this region is 

 generally compressed and, as a result, the utricles may present the 

 illusion in surface view of being thick- walled. 



The concept of this species as presented by Barton was broad, and 

 included both "stalked" and "sessile" plants such as discoidea. Hence, 

 the reported geographic range of cuneata has sometimes been consider- 

 ably extended as has been noted by Gilbert (1947), Papenfuss and 

 Egerod (1957) and Hillis (1959). 



Two forms of this species, f. digitata and f. undulata, have been 

 designated (Barton, 1901, p. 16, Plate 1, Fig. 9, Plate 2, Fig. 10), the 

 type specimens of which have not been located. However, since these 

 are based on "sessile" plants which are not included in the present 

 concept of the genus, they no longer seem applicable to H. cuneata. 



Halimeda scabra Howe 



Figure 37. 



if aZmetZascafera Howe (1905a), p. 241, Plates 11, 12 ;Collins(1909-1918),p.401; 

 Taylor (1928), p. 84, Plates 10, 11 ; Hillis (1959), p. 348, Plates 1, 5, 6, 8, 9. 



Plants generally compact forming cushion-like clumps, or somewhat 

 spreading, occasionally lax and decumbent and then to 25 cm in length but 

 more commonly not exceeding 9 cm ; calcification moderate ; colour on drying 

 bluish-green, olive or whitish, the surface dull and somewhat rough ; branching 

 frequent, usually dichotomous; basal segments often subcuneate, others 

 plane or slightly ribbed, most commonly subreniform to reniform but also 

 subcuneate and discoidal, to 11mm long, 20 mm broad and averaging 

 0-50-0-75 mm in thickness. 



Cortex of two to three layers of utricles with a fourth zone occasionally 

 present; outermost utricles remaining attached after decalcification, or 

 separating slightly but retaining their hexagonal shape as viewed from the 

 surface, each bearing a central indurated spine which may extend to two- 

 thirds the length of the rest of the utricle, 26-55 (-66) [xm in surface 

 diameter, (50-)70-165(-240) [j,m long in section including the spine, up to 

 seven supported by each secondary utricle ; secondary utricles 30-60(-70) [xm 

 broad, their length variable and often extending to the medulla; tertiary 

 utricles when present approximately 39-65 [jtm broad. 



Nodal medullary filaments united in twos and threes, the length of fusion 

 approximately 1-5 times the filament diameter or complete; resultant units 

 entangled and sometimes adhering for up to 60 y.m.. 



