1892.] MICROSCOPICAL JOURNAL. 187 



Plcurosigma Tcri-yaimm was the larger form mentioned in 

 previous article, and was found in a small pool in the salt marshes 

 of Morris creek; thorough search over several miles of neigh- 

 boring marsh and water tailed to find a single specimen else- 

 where, but I have since found what appears to be the same variet}' 

 in a ditch in the salt meadows of the Qiiinnipiac river, about eight 

 miles distant. A small shallow pool on the opposite side of 

 Morris creek contained P. strigostim^ with Sitrirella striatula 

 and .S". rcgi)ia; anotherneighboring pool had abundance of /*. 

 clongatinn. 



Plcurosigma A?nericamim was found in the creek, and I have 

 since found it in Stony creek and in Leetes' Island creek. It is 

 most likely to be mistaken for P. elongatum^ although very dis- 

 tinct aside from the striation. Dry mounts from a gathering from 

 Stony creek show b'oth forms side by side, and the characteristic, 

 dirterences are easily seen in the dry valves. P. Ainericaiitivi is 

 much larger and more robust, deeper in color, median line eccen- 

 tric and lighter in color than the rest of the valve. P. elongatjun 

 appears pale, thin, and flattened, median line more nearly central 

 and darker in color than the valve. P. paradoxiim is also 

 found in the creeks. 



The Actinocychis of Morris creek is A. Barklcyi. I find this 

 in many other sections of the Connecticut shore, in the Thames 

 river as far up as Norwich, and many points on Atlantic shore to 

 as fiir south as Florida, but the most abundant station is Morris 

 creek. This and many others mentioned in this paper do not 

 appear in " Wolle's Diatoms of North America." 



The small pools frequent in the salt marshes appear to be the 

 remains of former open water, which has been filled up by sedi- 

 ment and encroached upon by vegetation until only shallow pools 

 remain. These are almost without exception rich in diatoms, 

 and most of them contain abundance of the larger type of P. Bal- 

 ticum and very numerous varieties not often found elsewhere. 

 The salt marshes of Connecticut occupy the beds of ancient estu- 

 aries, and in all which I have examined below the surface peat is 

 found a deposit of clay and sand containing diatoms. This de- 

 posit is sometimes more than thirty feet thick and is horizontally 

 stratified in thin lamina in which the diatoms are very unequally 

 distributed ; contiguous strata frequently contain entirely difterent 

 forms, and below four feet depth they are generally deep water 

 marine forms, without admixture of brackish and shallow water 

 forms, so abundant at the top. These deposits, though not as an- 

 cient as those of Maryland and Virginia, will still date back to 

 glacial times, being probably the only fossil marine deposits in 

 New England. Of the very interesting varieties found in these 

 deposits I s^hall have more to say hereafter. 



The following determinations I quote from the series of J. 

 Tempere and H. Peragallo, though as they were made from small 

 samples of single gatherings they cannot show anything like the 



