266 JOURNAL OF CONCHOLOGY, VOL. I3, NO. $, JANUARY, igii. 



our valued Recorder, Mr. W. Denison Roebuck, that he had verified 

 that on the advent in any district in New Zealand of European niol- 

 lusks, especially of the field slug Agriolimax agrestis, the new arrivals 

 completely and quickly oust the native species, which have now to be 

 carefully searched for in the remoter parts of the bush ; and he said 

 that now-a-days half-a-dozen specimens would even in the best locali- 

 ties be an ample reward for a whole day's search, and this applies to 

 other forms of life, and, I may add, in a lesser degree to most other 

 countries, as even in the British Isles we possess many local and rare 

 species representing the weaker and dying elements ofovn- fauna, which 

 are being gradually restricted in their range and slowly exterminated. 



In commencing it may be remarked that the great sub-kingdom 

 Mollusca is a group characterized by the possession of a soft unjointed 

 body, covered with a moist skin, but destitute of any internal sup- 

 porting skeleton, as in man, or even an external one, as in the crab 

 or lobster, to give firmness and strength to the limbs; but this is 

 compensated for by its power to withdraw its soft body within the 

 strong calcareous shell, where it is secure from many enemies. 



Helix aspersa, or the snail, as it is familiarly called, is a representa- 

 tive species, and though so lowly and despised a creature, has not only 

 habits and peculiarities quite its own, but has also, contrary to the 

 popular belief, a wonderful and complex organization, with organs 

 physiologically and in some cases structurally quite similar to our 

 own, and in certain points is more specialized or, as some vv^ould say, 

 more advanced than man himself. 



Our H. aspersa is a comparatively modern species, probably evolved 

 since the deposition of the Miocene strata, as it is found in many of 

 the Pleistocene beds of Europe, but was unknown fossilized in this 

 country until discovered by Mr. Lewis Abbott in the Ightham fissure 

 in Kent, having previously occurred only in superficial deposits, in 

 primeval refuse heaps, or kitchen-middens, and in the ancient British 

 barrows or tumuli. 



It is now, however, one of the commonest of English snails, and is 

 an exceptionally interesting species, as representing the highest stage 

 of development which the Helices have attained in this or any other 

 country. 



It abounds in the south of England, l)ecoming rarer and more local 

 as we advance northward, its progress in that direction being hindered 

 by the great Scottish rift (now utilized as the Caledonian Canal), which 

 it has only succeeded in crossing at one or two points. 



This species was probably evolved in West Central Europe, and 

 has spread thevefrom chiefly to the west and south, its north-eastern 

 extension beiiig probably hindered by the competition of its close 



