MOLLUSCA. 129 



water on Sand Point, a single specimen of Goniobosis livesceyis which 

 was found on a board that had jirobably been washed from some other 

 habitat, and specimens of Goniobasis livescens and Physa ancillaria ob- 

 tained from the stone piers of a dock near Little Oak Point. The small, 

 lake forms of LampsUis luteola and L. ventricosa were very abundant all 

 along the coast, and a similar form of L. nasuta were also found, but in 

 lesser numbers; all of these were most abundant in places where the 

 water was .shallow for some considerable distance off shore, as at Twin 

 Bars. A few specimens of Unio gibbosus were obtained from Sand 

 Point and Stony Island, and single individuals of the small, lake forms 

 of Anodonta grandis footiana and Anodontoide^ ferussacianus subcyliyi- 

 draceus, and specimens of LampsUis recta sageri and Alasmidonta cal- 

 ceola were also collected, the fir.st three from Sand Point, the last from 

 Little Oak Point. 



6. Sand pools. As remarked under the description of habitat two, 

 most of the currents in this region come from the north; that is, their 

 general trend is southwest. This causes the sand beaches to be worn 

 away, more or less, to the east of points jutting north, while wide beaches 

 are deposited to the west of them. Also, the beaches to the east of 

 the.se. points are piled up by the action of the littoral currents during 

 storms, etc., so that they are relatively steep, while the sheltered beaches 

 on the western sides are low. On such beaches as the latter, where the 

 water is shallow for some distance off shore, the sand is piled up slightly 

 along the shore, while inside of this low. rounded ridge there is often a 

 more or less temporary lagoon. This relationship is caused, as is shown 

 at Oak Point, by a barrier beach, parallel to the shore, being formed in 

 shallow water by the drifting and pounding up of the sand, especially 

 during the high water produced by heavy storms, which shoal in time 

 landlocks the small lagoon left behind it. 



Sand pools are also formed by the currents blocking up the mouths 

 of small, intermittent brooks, which have washed out considerable de- 

 pressions in the beach during heaA'v rains. Pools formed in both wa}'S 

 have a similar fauna and apparently constitute but one habitat. The 

 water in these pools is usually strongly impregnated with iron obtained 

 probably from repeated evaporations. 



The flora of these pools consisted, in the main, of such sedges as 

 Juncus balticus; one pool had in addition several shoots of Sparganium 

 eurycarpum in it. The moUuscan fauna of these localities consisted 

 mostly of Lymnaea palustris and a small form of L. obrussa, the former 

 being very abundant. Succinea retusa and the form major of S. avara 

 vermeta occurred in and around several of them. 



These pools shift considerably with the ch'ifting of the sand. The 

 17 



