Nos. 620-621] THE HAWAIIAN CORAL REEFS 



423 



dredging is almost impossible, and diving is both labori- 

 ous and unsatisfactory. 



5. Reef -Rim.— Upon paddling across the lagoon to the 

 outer rim of the reef, one comes to shallow water, where 

 the heavy combers break and where wading is again pos- 

 sible. This zone is a favorite fishing-ground of the native 

 Hawaiians, as it abounds with plant and animal life. The 

 highest portions of the rim are usually exposed at low 

 tide; at high tide they are covered by 18-24 inches of 

 water. There are many table-rocks or shoals, with deep 

 channelways between. The rim is not regular or sym- 

 metrical; there are many indentations, crags, debris 

 slopes, pools, hummocks and sandy spots. Almost all of 

 the visible coral of this region is living coral, associated 

 with an abundance of corallines, bryozoans. hydroids and 

 red and brown algse. Some of the algal genera that are 

 confined largely to the outer reef-rim are: C odium, As- 

 parayopsis, Gymnogongnts, Porphyra, Turbitiaria, D'u- 

 tyota, HaUfseris, GeVidium, etc. Many of the species that 

 inhabit these turbulent and surf-churned waters are not 

 the tough, cartilaginous forms, but are very delicate and 

 fragile species, that apparently survive the wave action 

 because of their very delicacy. This is particularly true 

 of some of the finer red alga?. 4 



Highly important on the Hawaiian reefs are the coral- 

 line or stony alga? or nullipores. A number of genera— 



