THE TALUS-BRECCLA. DEPOSIT WITH LAND SHELLS.
At the southern base of Diamond Head, at a quarry not far from the terminus of the electric road (1905), is an extensive excavation in a talus-breccia of tuff with a calcareous cement. This carries shells of Lapachtinia, Helicona, Pitys, Suceinea, Pupa and Helix lamblata, as heretofore reported. A similar de posit may be found skirting the base of the cone, probably on every side as well as in the inside, but it is seen to the best ad vantage where the new road has cut into it between the quarry and the lighthouse. Near the lighthouse the specimens of shells are particularly abundant because of the greater magnitude of the excavations. To the list given above may be added Endodonta, and Professor G. H. Perkins found in addition, lower down the cliff, the remains of crustacea. Mr. C. Montague Cooke, of the Bishop Museum, has discovered additional localities of these shells upon Rocky hill and in Manoa valley, scattered among the uncemented talus blocks 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 : Lepachtinia, five or six species ; several of Amastra; Tornatella, two species ; Pupa; Endodonta, two species ; Helicina, one species ; Succhwa.
Mr. Cooke speaks of them as "subfossil." It remains to be de termined 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 hither ward 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 ex isting handsome 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 Limna-ea, as determined by anatomical characters ; the second a derivation from Buil/nu/its, because of conchological peculiarities.