NO. 1 TAYLOR: PACIFIC MARINE ALGAE 73 



HALIMEDA Lamouroux, 1812 



Plants moderately large, solitary, gregarious or forming spreading 

 colonies, with a massive rhizoidal base, a short stipe, and branched upper 

 portion or in colonial masses losing any distinctive base and attaching at 

 various places; branches segmented, the segments cylindrical or flattened, 

 circular or somewhat lobed, slightly to considerably calcified, except the 

 nodal joints between the segments. 



KEY TO SPECIES 



1. Branching characteristically in a plane; base remaining single 

 and distinct 2 



1. Branching in more than one plane, at least below; segments con- 

 siderably calcified ; base becoming obsolete . . . . H. Opuntia 



2. Segments lightly calcified ; viewed in transverse section the per- 

 ipheral utricles attached for a fourth of their depth or even more, 

 the subperipheral utricles several times larger ; the large segments 

 round to obovate H. discoidea 



2. Segments moderately calcified ; viewed in transverse section the 

 peripheral utricles barely attached at the surface, the subper- 

 ipheral utricles little larger H. Tuna 



Halimeda Opuntia (Linnaeus) Lamouroux 



Taylor 1942, p. 42. 



These plants, probably because of the depth at which they grew, were 

 somewhat more loosely branched than usual in the v. typica, but they had 

 the shape of the segments of that variety and not that of v. tripartita. 

 They show a little trace of ribbing and considerable tendency for the 

 branching to lie in a plane. A plant 18 cm tall and 25 cm in diameter was 

 secured. 



Mexico: Is. Revilla Gigedo, abundant as dredged from 50 meters' 

 depth off a bottom of gray sand at sta. 977 near I. Clarion, no. 39-24A, 

 16 Mar. 1939. Ibid., dredged from 45 meters, no. 39-32, 17 Mar. 1939. 



Halimeda discoidea Decaisne 



Taylor 1928, p. 82, pi. 10, fig. 17. 



Mexico : Is. Revilla Gigedo, occasional in tide pools at Sulphur Bay, 

 I. Clarion, no. 34-54, 5 Jan. 1934. Ibid., very abundant in tide pools on 



