TALUS-BRECCIA DEPOSITS 483 



hill and in Manoa valley, scattered among the uncemented talus hlocks 

 of that region, and in the surface soil. The geological age of all these 

 localities must be the same. The list of them, including a few collected 

 by Mr Cooke and identified by him, is as follows : 



Lepachti'nia, five or six species ; several of Amastra ; Tornatella, two 

 species; Pupa; Endodonta, two species; Helicina, one species; Succinea. 



Mr Cooke speaks of them as "subfossil." It remains to be determined 

 whether any of the species are extinct. 



This talus-breccia must be newer than the date of the eruption of the 

 tuff, because it is the same material, detached from the cliff by gravity 

 after consolidation. The cementing substance may be either fragments 

 of lime in the tuff or blown sand from the seashore ; and there must have 

 been quite an interval between the ejection of the tuff and the presence 

 of the animals, because the base rock must have suffered disintegration 

 so as to allow the growth of herbs and small trees and the migration 

 hitherward of the Mollusca. This interval was probably the same as the 

 one indicated at the Punchbowl and at Moanalua. 



It is highly probable that these shells represent a late stage of the 

 Pliocene, partly because they seem to be older than the existing hand- 

 some species of Achatinellidae and partly because of the presence of a 

 marine deposit overlying the quarry mentioned above. Two views of the 

 origin of the Achatinella have been promulgated — the first, that of 

 Professor Pillsbry, that it has come from a type analogous to Limncea, as 

 determined by anatomical characters; the second of a derivation from 

 Bulimulus, because of conchological peculiarities. 



The latest Submergence and Eeelevation 



It would seem as if there must be evidence of the submergence of Oahu 

 after the accumulation of the talus-breccia to the depth of 250 feet. The 

 relation of the deposit to the talus-breccia may be seen at the quarry, 

 where at the altitude of about 40 feet there is a red earth with many 

 marine remains directly overlying the talus-breccia. Beside the mol- 

 lusca, there are corals and remains of fish. This is the only place where 

 the relations of these shells to the talus-breccia is clear. What seems to 

 be the same material rises to 200 feet at the north base of Diamond head 

 and also at lower levels. I do not recognize anything like a shoreline, 

 but the marine shells are frequent. Near Doctor Wood's summer house, 

 near Kupikipikio, are Cypreas and Turbo, both shells and opercula. 

 The surface is strewn with rough blocks. The shells are seen when the 

 lava fragments are thrown to one side in a very red earth, the residuary 

 remains of the Kaimuki lava. 



