98 L. HILLIS- COLIN VAUX 



Halimeda monile (Ellis and Solander) Lamouroux 

 Figure 24. 



Corallina monile Ellis and Solander (1786), p. 110, Plate 20, Fig. c. 

 Halimedea monile Lamouroux (1812), p. 186; Halimeda monile Lamouroux 



(1816), p. 306; Howe (1907), p. 501; Collins (1909-1918), p. 399; Taylor 



(1928), p. 82; Hillis (1959), p. 371, Plates 4-8, 12. 

 Halimeda incrassata v. monilis Harvey (1858), p. 24; Borgesen (1911), p. 138 



Borgesen (1913), p. 112. 

 Halimeda incrassata v. monilis f. cylindrica Borgesen (1911), p. 143, Fig. 10 



Borgesen (1913), p. 113, Fig. 91. 

 Halimeda incrassata v. monilis f. robusta Borgesen (1911), p. 143, Fig. 9 



Borgesen (1913), p. 113, Fig. 90. 

 Halimeda incrassata f. monilis Barton (1901), p. 27, but not Plate 4, Fig. 40. 



Plants sometimes elongate and sparsely branched, but more commonly 

 compact and robust, to 16 cm tall excluding the holdfast which may extend 

 to 4 cm in length; calcification moderate, becoming heavier towards the base, 

 branching mainly ditrichotomous ; basal first to second segments forming a 

 short stipe, generally cylindrical to subcylindrical but becoming almost 

 semicircular in densely branched plants, these supporting two to several 

 segments which may consolidate laterally into a modified fan- shaped 

 structure; other segments plane or ribbed, generally trilobed with terete 

 arms, or cylindrical, the former usually predominating in regions of branch- 

 ing, the latter in the upper part of the plant, cylindrical ones to 8 mm long, 

 3 mm broad and averaging 1-5 mm in diameter, others excluding the modified 

 basal ones to 8 mm long and 8 mm broad. 



Cortex of three to five layers of utricles; outermost utricles remaining 

 attached after decalcification for an average distance of 6 yua, (23-)30- 

 60(-74) [xm in surface diameter, 48-95(-116) [im. long in section, two or 

 four supported by each secondary utricle; secondary utricles 23-70 (xm 

 broad, 23-100(-140) [xm long; tertiary utricles 30-90 [xm broad. 



Nodal medullary filaments usually uniting in twos, threes or larger groups 

 for a distance of approximately 49-80 (xm, these units held together by 

 short narrow tubular processes which are easily broken; filament walls 

 thickened and pigmented. 



Type specimen. Collected by Ellis in Jamaica; according to 

 Barton (1901) this plant has been lost. 



Habitat. Grows in sand, mud or other unconsolidated substrate, 

 from near low-tide line to about —13m and possibly deeper. In 

 water of about 0-3 m depth, low tides, it may form exceedingly 

 dense stands, and one Jamaican quadrat I counted had 360 com- 

 pressed monile thalli per square metre, together with 140 flattened 

 incrassata thalli. Such dense growth may be restricted to very 



