16 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



morphosed remnant to represent the pre-existent land now showing 

 merely as chalcedonic blocks littering the razorback as it extends S-like 

 on the surface of the sea. 



Basal rocks or basal limestones are of unfrequent occurrence. At 

 Mba Vatu — the northern division of Vanua Mbalavu — huge stratified 

 limestones occur as high as 250 to 300 feet above the sea. To the north 

 of these dipping limestones the land is occupied by " terraced " forma- 

 tions, and to the south it abuts on a great andesitic massif. Fourteen 

 miles south the coralline limestones lie unconformably on a bedded red 

 laterite. 



At Tuvutha and Mango a very decomposed conglomerate or agglom- 

 erate of andesitic origin underlies a bright red limestone in the case of 

 Mango and white limestone in the case of Tuvutha. The cementing 

 material is very calcareous. These rocks bear the stamp of great age, 

 aud have evidently a great development beneath the coral islands. 



The Geological History and Topography. 

 The Main Islands. 



The General Topography. — The topography of southwestern Viti 

 Levu is characterized by numerous almost perfect cones, with smaller 

 cones on their slopes. 



In the Namosi, or central district of Viti Levu, sharp knife-like sum- 

 mits and aiguilles rise to 3000 and 4000 feet above the sea. These yield, 

 on disintegration, fertile soils, especially in the valleys. 



The great dolomites of the Singatoka River constitute a decided topo- 

 graphical feature. They rise almost perpendicularly with exceedingly 

 large and sharp projections in the upper half, the result of long-con- 

 tinued erosion. From the base the strata rise straight as masonry for 

 400 or 500 feet ; above that they become more or less broken. They 

 appear to be exposed in part by the removal of softer overlying strata. 



The Singatoka River itself has changed its course, and viewed from 

 the huge tilted dolomites dominating the river, its old bed, now about 

 50 feet above the modern stream, constitutes a marked feature in the 

 scenery. 



Coastal Topography. — The coastal topography of the larger islands 

 consists in the main of cliffs of elevated and shelly limestones of ancient 

 date, scattered amongst huge rolling slopes of volcanic hills extending 

 seaward. . In these elevated shelly strata reefs of undoubted coral origin 



