108 BULLETIN : MUSEUM OF COMPAEATIVE ZOOLOGY. 



Islands has a crater with a depth of nearly 450 fathoms^ ■nhile manv 

 smaller peaks, some of fully 1,200 feet rise from its bottom, and its 

 diameter is fully as great as that of many of the larger atolls of the 

 Fijis. So that, at any rate in a volcanic district, the great depth of 

 some of the atolls cannot now be considered as a proof of the theory of 

 subsidence. 



A still larger extinct crater than Haleakala is that of Aso San in Japan, 

 and in Java there are many craters of dimensions fully equal to those 

 of a number of Fiji atolls. 



In addition to ThomV)ia and Totoya, we found at Moala the rim of an 

 extinct crater forming the deep bay on the east side of the island (Plates 

 16, 56). The longest diameter of this crater must have been fully 

 three miles, and had the denudation of the island been carried on some- 

 wliat further, so as to eat away the low western rim of the crater (Plate 

 56) and connect the deep ba}' of the east face (the extinct crater} with 

 the indentation on the west of the island, it would be difficult to detect 

 the existence of a former extinct crater from the narrow ridge or island 

 which would rise in the eastern part of the lagoon (Plates 16, 56). 



Kramer-' has attempted to account for the elongated outline of so 

 many of the atolls of the Paumotu, Caroline, Marshall, Gilbert, and 

 Ellice Islands, upon the theory that they owe their origin to submarine 

 hot springs and volcanic eruptions, the material of which was distributed 

 by the trend of the great oceanic currents in the general directions 

 indicated by these island groups. 



While granting that volcanic agencies have raised the coral islands of 

 the Pacific, we must remember that the shape of the islands and their 

 extent are due to the size of the plateaus of submarine erosion which form 

 tlie banks upon which coral reefs have grown. Undoubtedly the sub- 

 stratum of many of the atolls may have been formed of volcanic ashes by 

 eruptions similar to that which has thrown up Falcon Island, and which 

 has been fully described by Lister.^ Yet the great majority of the vol- 



1 Bau d. Korallenriffe, p. 88. 



- J. J. Lister, A Visit to the newly emerged Falcon Island. Tonga Group, South 

 Pacific. Proc. Tloy. Geog. Soc, 1800, Vol. XIL p. 157. 



The island (Falcon) is composed of fine-grained dark grayish material, arranged 

 in strata. " A bare brown heap of ashes round wliieh the great rollers break and 

 sweep the black shore in sheets of foam." The eruption occurred four years ago ; 

 its present heisht is 153 feet. " Considering how rapidly the island is being covered 

 by the action of the waves, it is evident that in a few years ... it will have disap- 

 peared beneath the surface of the ocean. . . . Some distance to the east of it lie two 

 islands, Namuka iki and Mango, and these islands have been elevated before any 



