68 THE NAUTILUS. 



young, small shells, which I will place in some water suitable for 

 their growth and pi'opagation. Among the rest are two or three of 

 good size, while all are well suited for the cabinet. 



The largest example I have observed is an imperfect dead valve, 

 which, with its other half, measured originally as follows : Trans- 

 versely, 6| ; vertically, 3g ; and in thickness 2$ inches. I have no 

 doubt that some have been found of still larger dimensions ; was 

 told that such had been taken, but after diligent inquiry failed to 

 get trace of them. 



Regarding the place of their occurrence, I can give the following: 

 About two and one-half miles south of Dover Plains, on the farm 

 of Mr. Geo. Preston, is a swamp near the outlet of which a con- 

 siderable quantity of peat w\as dug thirty or more years ago. The 

 hole thus formed is about 100 feet by 40 in length and breadth, 

 and 4 feet deep, and serves as a basin to collect some of the drainage 

 of the marsh, it being filled with water and perhaps three feet of 

 black mud deposited during the intervening time: from this is 

 raked in limited numbers specimens of this Anodon, extraordinary 

 for their luxuriant growth and beautiful coloring. 



That this whole tract of about twelve acres was originally a 

 shallow lake there is no question. Its former outlines are seemingly 

 well defined ; it lies encircled by hills of upturned calcareous and 

 micaceous rocks ; a narrow opening on the north has afforded an 

 avenue of escape for its imprisoned waters. The swamp has no 

 inlet but is springy over its entire surface, and at present is over- 

 grown with shrubbery and small trees. Its outlet is a small ditch 

 which empties into the Weebutook, or Ten Mile River — a tributary 

 of the Housatonic. about three-eighths of a mile distant, making a 

 descent of fifty feet in its course. Underneath the stratum of peat 

 is a bed of marl a couple of feet in thickness, consisting of fresh- 

 water shells — species of Sphaerium, Limnaea, Physa and Planorbis, 

 ivhich lived ages ago. 



Whether any of these bivalves were noticed while digging peat, 

 is impossible to say, but believe it is only eight or ten years since 

 they have attracted attention, and this because the muskrats were 

 liringing them to light ; many recently broken shells are lying about 

 the shore — brought up by these rodents. 



I could not find any other fresh-Avater shells in the pond, but 

 obtained about the marsh (piite a number of interesting land-snails, 

 iiniong them the following : Mesodon albolabris, M. thyroides, 



