Adams. — Land Mollusca of the Thames Ooldfields. 177 



Aet. XX. — The Land Mollusca of the Thames GoMfields. 



By James Adams, B.A. 



[Read before the Axickland Institute, lith November, 1886.] 



It will surprise many of those who spend a large part of their 

 lives in the forests of New Zealand to learn that there are a 

 great number of land-shells in the bush. These shells, how- 

 ever, are in general so small and so inconspicuous that they 

 are only found after a careful search, although every forest has, 

 perhaps, thousands of at least forty different species. They are 

 not only overlooked on account of their small size, but they 

 hide also under leaves, or under the bark or in the crevices of 

 the trees. 



A few of the larger ones are, of course, well known in the 

 localities where they are numerous — such as Panjphanta 

 hishiji, and Rhi/tida (jreenwoodii — but the greater number 

 range in size from that of a pea to a pin's head. Indeed, one 

 of them, and not the smallest, has a Latin cognomen that 

 means "pin's head." There are at present known to science 

 about one hundred and twenty of the Land Mollusca of New 

 Zealand, and these have been classified and described by 

 Captain Hutton in a paper in the sixteenth volume of the 

 " Transactions."* 



It occurred to me, when collecting land-shells for him and 

 for my friend Mr. Cheeseman, that it might be useful to make 

 a list of the species found in the Thames District, and to men- 

 tion at the same time the most favourable localities for searching 

 for them. In one respect the land-shells are deserving of more 

 than a passing attention, and that is the surprise that every 

 one must experience in finding them at all in New Zealand. 



They are easily drowned in fresh water, and salt water is 

 sudden death to them. They cannot bear exposure, as they 

 quickly disappear from even rude clearings ; and yet our 

 laud-shells have their nearest relations in Tahiti, Samoa, 

 and the Solomon Islands. Countless ages must have elapsed 

 while such slowly-moving animals gradually spread over the 

 intervening space between such distant countries. Indeed, 

 their great antiquity is confirmed by the fact of finding fossil 

 land-shells on a fossil tree in the Palaeozoic rocks. It may be 

 supposed that, when forests flourished on the oldest sedimentary 

 rocks of New Zealand, the ancestors of the present land-shells 

 swarmed under the dead leaves and on the tree trunks. 



* " Trans. N.Z, Inst.," vol. xvi., art. viii. 

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