A Few Notes on some Land Shells (Achatinella) from 

 the Sandwich Islands. 



By W. T, Manger. Read Feb rua7y 12,^/1, 1902. 



These beautiful little shells are of very great interest, inasmuch as 

 they are found only in the Sandwich Islands (with the exception of 

 one or two very small species). They occur in most of the twelve 

 islands of the group, which lie in the North Pacific in mid-ocean, 

 between the coasts of Asia and America, but are nearest to the 

 American coast, from which they are about 2100 miles distant; and 

 consequently their natural history has many special features of its 

 own. These shells have an especial claim to the honour of being 

 ranked as a genus ; they are mostly of uniform size and substance, 

 and are characterised by the same plan of convolution of six to seven 

 whorls ; never umbilicated ; by a similar design of colouring, and by 

 a peculiar structure of the columella. The species are nearly all 

 small, and many of them are both dextral and sinistral ; some are 

 found on trees and shrubs, whilst others are always met with on the 

 ground. 



It is very remarkable that the average range of these species is so 

 restricted as it is ; in some cases it is only two or three square miles, 

 and only very few have the range of a whole island ; it is even said 

 that each valley possesses its own peculiar species. Kew, in his 

 "Dispersal of Shells," says, "The Achatinella of the Sandwich 

 Islands, so remarkable for limited specific areas, have in all proba- 

 bility been occasionally carried by accidental means into the midst 

 of each other's districts, but, as their distribution clearly indicates, 

 they must generally have failed to establish themselves in the new 

 surroundings, being unable, no doubt, to compete successfully with 

 those already in possession." Speaking of distribution, the inquiry 

 naturally forces itself on us, how did these animals get to the Sand- 

 wich Islands, which are of volcanic origin and 2100 miles from the 

 nearest continent, and that none succeeded in getting to other 

 places, or, at least, have not been discovered in other places, whilst 

 other families, Helicidce, for instance, are found in every country and 

 nearly every island in the world ? Mr. Wallace has maintained that 

 all the animals now inhabiting truly " oceanic islands " must have 

 reached them by crossing the ocean, or be the descendants of 

 ancestors which did so, for such islands have been produced in mid- 

 ocean and have never formed part of a continent. Quoting again 

 from that work, " The Dispersal of Shells," it is suggested that the 



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