294 



L. HILLIS- COLIN VAUX 



Pass between 

 Lojwa( north) 

 and Alembel 

 (south) 



Mut B1,3 

 C3,5 



(S.Medren) Pinnacle C2,5 



T(60-90') 



B2 

 Pinnacle C2,5 



T(25-30') 

 A2 

 B1 



Wide Pass ^^'^ 



• Japton 



B1 



C2,5 Medren 



Enewelak 



Osp. 



Fig. 97. Map of Enewetak Atoll showing stations visited for Halitneda project, 1975, and 

 their Halimeda and Tydemania species. Halimeda species: Al = incrassata, A2 

 = cylindracea, A3 — stuposa; Bl = opuntia, B2 = copiosa, B3 = distorta, B4 = 

 minima; C2 = gigas, C3 — gracilis, C4 = lacunalis f. lata, C5 = m,acrophysa, 

 C6 = taenicola; Dl = inicronesica, D2 = fragilis. TydewMtiia species: T = expedi- 

 tionis. (Modified from Hillis-Colinvaux, 1977.) 



and Harrison, 1977), it is better called the fore-reef terrace. Proceeding 

 shoreward a spur and groove region is encountered, and breaking the 

 surface at low tide is the algal ridge. Development of spur-groove and 

 algal ridges vary considerably, however, and they may be absent. The 

 spur-groove system is best developed on the windward sides of atolls ; 

 on the lee side smooth margins are the pattern (Tracy et al., 1948). 



The algal ridge has traditionally been called the " Lithothamnion 

 ridge", and the component algae referred to as Lithothamneae or 

 "nullipores". The name is a misleading one, however, brought about in 



