ON" THE LAND MOLLUSC A. 
21 
and find in tlie chalk, wherever it comes to the surface, and in the 
water of the numerous streams which rise out Of the chalk, calcareous 
material in plenty with which to form their shells. These conditions 
still prevail to a great extent, and we may still expect to find in 
abundance in our woods the species which have not so far changed 
their habits as to roam about in the open country ; a careful search, 
also, for the species which follow man, frequenting the cellars of 
houses, the vicinity of cottages where they would thrive bn the 
refuse thrown out, nursery-gardens, and cultivated fields, may also 
be richly rewarded. There are, on the other hand, some few 
species which only thrive in proximity to the sea, imbibing moisture 
from its spray, and which are therefore not likely to be found in 
Hertfordshire. 
It must be evident from what has already been said of the 
distribution of our terrestrial Mollusca that, as with all other 
creatures, different species have different habits and frequent dif¬ 
ferent situations. It may be well to enquire a little more closely 
into this diversity, to have some guide as to where best to look for 
certain forms, and at the same time to learn something more of the 
habits of the members of the different families. 
The Aeionidh: and Limacld^ will be searched for with the 
greatest chance of success early in the morning from spring to the 
commencement of winter. Some may be found occasionally on dry 
exposed ground, but marshy places and moist shady woods are more 
frequented by them. In mild and humid weather they may be 
seen on footpaths, under hedge-rows, and on the trunks of trees. 
In woods they hide in moss growing on the ground, on stones, and 
on trees, and some may be found under the bark of trees, or 
wherever there is a crevice into which they can creep, and also 
under the larger fungi, upon which they sometimes feed ; but here, 
as elsewhere, no stone should be left unturned. All the species are 
believed to have the power of suspending themselves by a thread of 
mucus from the branches of trees, but, unlike spiders with their 
thread, they have not the power of drawing it in, and therefore 
when once suspended they must reach the ground or something in 
their way before they can free themselves. 
The Testacellidhj are essentially nocturnal animals; they can 
seldom be found above ground except at night when quite dark, 
and they are most frequently met with in spring. They are 
burrowers, and are the only predaceous species amongst the land 
mollusks. They feed chiefly on earthworms, and are therefore most 
frequently met with in gardens and highly-cultivated ground, 
where their prey most abounds. During the day they remain 
either under the surface of the soil, usually some distance down, or 
under large stones. 
The habits of the Helicidh] are very varied. Succinea and 
Vitrina chiefly frequent the margins of streams. The Succinece are 
in fact almost amphibious ; they occur in numbers on plants grow¬ 
ing in the water, such as species of Typha , Nuphar , and Sparganium, 
and may sometimes be found high up on the stems of these plants 
