40 BIOLOGICAL SURVEY OF 



Venus niercenaria has never been reported in Maine north 

 of Casco Bay, though a common species of the shallow south- 

 ern and warmer regions of the eastern coast of Canada ; and 

 yet at one time it must have been fairly well distributed on 

 the sand beaches. It has gone with the sand beaches and is a 

 striking example of the changes that go on in the fauna of a 

 region even within the lifetime of an individual. Expert 

 opinion put the age of the animal we took at 40 years, and so 

 about 40 years ago the sand beaches which are now covered 

 with mud must have been exposed, for this animal could not 

 have lived there and reproduced. They could have lived 

 there, as some of them have for many years, but they would 

 gradually die out, for the spat could not live in the mud. 

 About 50 years ago heavy cutting of timber took place on the 

 upper reaches of the three branches of Union River, and the 

 subsequent burning and erosion filled this river with silt and 

 is still filling it, and the result has been a gradual covering of 

 the beaches and filling up of the inner bay by the soft mud 

 carried down. This mud is so soft that from certain places 

 in the Bay a fine mesh dredge holding two bushels can be hung 

 in the water at the surface and towed around and washed out, 

 and there will not be more than a handful of old shells left. 

 It is practically barren of life. The same thing is true of 

 parts of Somes Sound. This Sound is full of mud from one 

 end to the other and in one or two places there are ridges or 

 peaks extending up from the bottom that rise like small 

 islands above the level of the mud. On these are found the 

 more common forms, while elsewhere in the Sound, particu- 

 larly in the upper part, there are large areas almost devoid 

 of life. 



The one sandy beach of the Island is on the eastern side 

 and faces toward the south. Contrary to what one would 

 expect, this is a very barren locality, for the southern storms 

 drive the shells in toward it and break them up and the con- 

 stant movement of these shells really grinds the life out of 

 everything that would be there. The sand itself is composed 

 almost entirely of finely ground shells. The nearest beach is 

 about 30 miles north of the mainland. 



