254 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



the east face a former gap or passage, now closed, is indicated (PI. 224, fig. 3). 

 This low part of the land rim is quite distinctly seen from the western face 

 of the land rim. The island is an interesting one ; it was considered by 

 Dana to be perhaps the most typical of the atolls he visited. At Maraki 

 nothing indicates that the island has ever been subjected to subsidence. 

 On the contrary, the immense amount of material tin-own up, both on the 

 east and on the west face, forming the land rim of this atoll, clearly shows 

 the manner in which the land rims of the atolls of the Ellice and Gilbert 

 groups have little by little been accumulated. It is only when we examine 

 such a small atoll as Maraki that we can take in at a glance the changes 

 that have taken place on the underlying platform which has supplied in part 

 the material for the coarse shingle beaches ; the dead and decaying corals 

 fringing the outer reef flat, and the material derived from the subsequent 

 disintegration of the beaches of conglomerate and breccia supplying the rest. 

 This is well seen on the west face, north of the boat passage, where huge 

 bouldei's of conglomerate form a shingle beach (PI. 147, fig. 2) extending 

 along the greater part of the northern extremity of the west face. On the 

 western side of the lasfoon masses of beach rock conij-lomerate are found 

 cropping out at the surface (PL 146, fig. 3) ; they form the underlying base 

 of the narrow line of islands and islets parallel to the outer land rim, a line 

 defining the inner margin of secondary lagoons (Pis. 149; 150, fig. 2) so 

 characteristic of the Gilbert and Ellice Islands, and so well developed at 

 Taritari and Tarawa. 



Near the southeast point of Maraki^ (PI. 146, fig. 2) the reef flat slopes 

 gradually to the outer edge. This is marked by huge knolls of Nullipores and 

 of Pocillipores, forming an outer barrier to the shallow pool which extends 

 from the outer edge of the reef flat towards the base of the beach of the 

 main land rim (PI. 146, figs. 2, 3). The beach rock flanking the base of the 

 high and steep beach of Maraki is of a brilliant brownish yellow ; its patches 

 extend as large slabs "over the reef flat and partly up the slope of the high 

 beach, form a belt of brilliant color, in strong contrast with the white coral 

 sand and the light yellowish mud which covers, in places, the bottom of 

 the platform lagoon enclosed by the outer knolls (Pis. 147, fig. 1 ; 14S ; 



1 A. Cliart 732. 



