128 Rhodora [AuGuST 
below it which rose up in-great banks on each side of the railroad. 
All this material contained diatoms, and some of it was very rich, 
especially in number and rarity of species. I dug up material from 
about twelve feet below the surface, and found a stratum rich in the 
beautiful Surirella Febigerii Lewis and other rare kinds. One pound 
of this earth furnished diatoms enough to make several thousand 
slides, each slide containing thousands of diatoms. The marine 
deposit in these marshes is sometimes near the surface, and is thrown 
out in digging ditches, and always in quantities in preparing the 
foundations for the abutments of bridges. From the earth thrown 
out in digging a post-hole for a fence on the margin of the marsh near 
Branford Station I procured a supply of Campylodiscus echineis 
Ehrenb. The Quinnipiac marshes are large, and along their western 
margin is a series of clay pits from which the tide water is kept out by 
dikes. The diatomaceous deposit here is of no great thickness but has 
a very interesting collection of species. At Davis pit the clay is 
covered by a layer of sand, upon which rests a stratum of alluvium, 
which contains fresh water diatoms exclusively; these are mostly 
decayed and broken, those entire being chiefly Navicula lata Bréb., 
with a few of the large Stauroneis acuta and Navicula Semen Ehrenb. 
Upon the alluvium is a mass of loam containing the roots and stumps 
of trees with their trunks and branches beside them, the whole covered 
with the marine deposit, which extends upward through about four 
feet of coarse peat. 
At many places along the Connecticut shore the ancient marine 
deposit projects through the bank of sand forming the beach, and is 
visible at low tide, the huge bank of sand being a superficial structure 
cast up by the sea and resting upon the ancient deposit. All these 
salt marshes were once open water, and the sea is now coming back 
upon them and swallowing up the land. Some of the pond holes in 
these marshes are deep, with a bottom of soft mud; these are often the 
remains of former open water, and are always rich in diatoms, fre- 
quently very different from those of the neighboring waters. Here 
is the home of the large Pleurosigma balticum, the very large Amphi- 
prora pulchra Bail, the larger type of Surirella striatula, Scolio- 
pleura, Amphora, and a variety of rare forms. 
In a pond hole of the marshes of Morris Creek I found a new 
Pleurosigma, quite large, in Morris Creek another, not quite so large. 
On the rocks near the tide gate were masses of Melosira Borreri Grev., 
