68 THE NAUTILUS. 
young, small shells, which I will place in some water suitable for 
their growth and propagation. 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, 63; vertically, 82; and in thickness 22 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 was 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 les 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, 
which 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 
bringing them to light; many recently broken shells are lying about 
the shore—brought up by these rodents. 
I could not find any other fresh-water shells in the pond, but 
obtained about the marsh quite a number of interesting land-snails, 
among them the following: Mesodon albolabris, M. thyroides, 
