146 MOLLUSCA. 



to the trees found in the damper woods, basswoods and oaks are quite 

 abundant, and, in one Hmited area, there are considerable numbers of 

 white pine. 



This habitat was only studied on Stony Island. There, Polygyra al- 

 holahris, P. thyroides, P. vionodon, Pyramidula alternata, Pallifera dor- 

 salis and Agriolimax agrestis were very abundant; and a few specimens 

 of Zonitoides arhorea, and a single juvenile individual of Polygyra multi- 

 lineata were also obtained. Polygyra albolahris was much more abund- 

 ant here than in the preceding habitat, while P. multilineata, on the 

 other hand, was almost entirely wanting. 



32. Dry clearing. On account of the shallowness of the soil on these 

 islands, all of the clearings are very dry. Grasses are the only plants 

 that appear to be able to hold their own here, with the exception of the 

 sumachs, which are of large size and cover considerable patches of 

 ground. In these places a few shells were found which had taken refuge 

 under boards and in a stone pile, from which they probably come out 

 during rains and heaw dews. 



Under a stone-pile in this habitat, a number of specimens of Pyra- 

 midula alternata and Polygyra monodon were obtained. A single in- 

 dividual of Polygyra albolahris was also obtained under a plank. 



33. Rocky beach. A few shells are to be found on the bare rocks of 

 the middle beach, in protected places under driftwood and rocks where 

 a little soil has gathered. The fauna of these places is most probabl}^ 

 temporary, as the ice in the winter months sweeps these beaches clean. 

 A few molluscs may be able to winter in the deeper crevices of the rocks, 

 but it appears that the main portion of the fauna must be derived an- 

 nually from the woods adjacent to the beach; snails may also be washed 

 ashore as mentioned in the discussion of the sand beaches in the sand 

 dune region, but in this case this would not be necessary for their re- 

 stocking, as woods with considerable molluscan life are in direct con- 

 nection with these beaches. (PI. XIV.) 



Polygyra albolahris, Pyramidida alternata and Succinea retusa were 

 obtained from these localities. The first two were present in ciuite con- 

 siderable numl)ers. 



34. Sa7id beach. Land molluscs also occur in considerable numbers 

 on the middle beach along the sandy portions of the shore of these two 

 islands, especially where the beach is partially protected, as along the 

 southern shore of North Island. These sand beaches appear to ])e more 

 favorable to molluscan life than the rocky ones discussed under the 

 preceding habitat, perhaps because the sand beaches are formed in the 

 protected places — the ones most suitable for the life of the snails. The 

 fauna of these places is probably destroyed during the winter as are 

 those of the preceding habitat and habitat twenty-five; and they are 



