6o HENSHAW : SE.MI-FOSSIL SHELLS IX HAMAKUA DISTRICT, HAWAII. 



That the deposits of fossils are confined to the two localities in c|uestion 

 is not for a moment to be believed. A well-worn trail at Palihoukapapa, 

 and some deep holes dug by cattle at Mana, chanced to reveal the presence 

 of the shells in these two localities ; but no doubt there are similar deposits 

 in many other places on the Waimea Plains and elsewhere in the northern 

 end of the island. Indeed the author has heard that in the district of 

 Kohala such deposits are by no means uncommon. 



In a paper published in 1887 (Hawaiian Annual), Mr. 1). D. Ikvldwin 

 speaks of extensive portions of the Hamakua and Kona districts at altitudes 

 of 3,000 to 5,000 feet, " where the soil is filled with millions of sub-fossil 

 shells of this [Succinea] family." In a recent letter to the writer, Mr. Bald- 

 win mentions these deposits more in detail, and states that he made several 

 hurried trips to the region above Honakaa and in the vicinity of Waimea 

 in the years from 1865 to 1872 and again in 1878. In all of the open 

 country above the forest, the ground was " white with dead Succineas and 

 probably other shells. The shells were (juite even))- distributed through 

 the light surface soil.'" Later, through the agency of floods, the surface 

 shells here mentioned may have been swept into pockets and so formed 

 deposits similar to those examined by the writer. 



Indeed, in several specimens of tSuccinea, faint traces of colour are still 

 visible, the original deep red or maroon having faded to pink. The same 

 is true of some of the smaller shells. 



In a climate like that of Arizona and in dr\- earth uveu frail shells 

 might l)e preserved almost intact for several hundred years; but the climate 

 of the ^^'aimea plains is l)y no means a dry one in this extreme sense. Heavy 

 dews are the rule all through the }ei*i', and rains are probably frequent 

 enough to keep the humus damp all the time excejjt in seasons of drought 

 when it is likely to dr}- for a few inches only from the top. That frail shells 

 like the Sturinea-f could long be preserved in damp and porous humus, even 

 though a foot from the surface, is not credible. All things considered, it 

 does not seem likely that the fossil shells date back more than a century, 

 and it is i)robable that they and the forest perished at the same, or nearly 

 the same time. 



As to some extent confirmatory of the theory of the recent age of the 

 shells, the writer has recently learned that about fifty years agc^, more or less, 

 an extensive forest fire raged in this section, and this may have been the 

 cause of the simultaneous destruction of such vast quantities of moUusca. 



The following Sacrineas are believed to be undescribed species. All 

 four are without doubt extinct in the region in question. 



In examing several thousand specimens of these semi-fossil /Succineas, 

 one cannot fail to be impressed with the considerable diversity in shape and 

 size of individuals, presumably of the same species. The difficulty in treating 

 such matei ials consists not in the finding of new species but rather in the 

 exercise of due restraint in naming forms evidently closely related to living 



