185 



In the families Cyclostomacea and Colimacea are included the extensive 

 series of Laud Snails, which, since Lamarck's time, has increased from 

 about two hundred and fifty species to upwards of five thousand. The 

 conchologists of Germany, more especially Dr. Pfeiffer of Cassel, owing 

 perhaps to their inland position, have worked almost exclusively during 

 the past ten years upon land shells ; and encouragement has been given 

 far and wide to travellers, particularly to plant-collectors, in all countries 

 to look well after Snails. The researches of Mr. Cuming, both in the arid 

 plains of Chili and in the rich woods of the Philippine Islands, have added 

 to our stores of land shells to an extent almost unprecedented in any 

 branch of natural history ; and many scarcely less zealous collectors have 

 contributed to enrich our cabinets from the vast territories of Brazil, 

 Bolivia, and Venezuela, and from India, Australia, and the Western Isles. 

 It may seem strange that natural history should have occupied, more or 

 less, the attention of men's minds since the time of Aristotle, and that the 

 land snails, the most readily accessible of all shells, should have so long 

 dwelt in obscurity ; but the philosopher might ask, with nearly as much 

 show of reason, how comes it to pass that the world has existed for more 

 than six thousand years, — according to Baron Bunsen, twenty thousand, — 

 and it is only now that we have discovered the use of steam-engines, elec- 

 tric telegraphs, and lucifer matches. Snails, of one sort or another, in- 

 habit all lands, and being of sluggish habit the types of form are very 

 local. Who then shall say that even the number of species known up to 

 the present time is not very far short of the actual existence of mollusks 

 on land, seeing that they scarcely amount to the average proportion of 

 a single species to every area of 2000 square miles ? 



The Cyclostomacea, numbering, according to the latest conchological 

 census, about 1150 species, differ from the great bulk of the land shells 

 included under the head of Colimacea, in being operculated and inclining 

 to amphibious habits. They affect damper situations, and some live par- 

 tially in water. Dr. Pfeiffer distributes the Cyclostomacea into forty-three 

 genera, indicated in our lists of species as subgeneric divisions of the fol- 

 lowing : — 



Helicina. Cyclostoma. Teuncatella. 



Stoastoma. Plpina. Geomrlania. 



Genus 1. HELICINA, Lamarck. 



Animal ; similar to that of Cyclostoma. 



Shell ; depressly globose, with the spire mostly rather sharp, gene- 

 rally smooth; aperture semiorbicidar ; lip reflected, sometimes 



2 B 



