594 NEW YORK STATE MUSEUM 



penetrate the clay, absorbing water from it and rejecting the 

 contained lime, which deposits itself around the root forming the 

 hard rhizomorph. Their interior structure is crystalline. 



Another form of concretion is found in the delta sands at Croton 

 point. It consists of botryoidal masses of sand, cemented by oxid 

 of iron. Some of them show the layers of deposition of the sand. 

 The concretions are usually small, but one mass was noticed fully 

 6 feet long and 4 feet wide. 



Concerning the origin of these concretions various opinions are 

 expressed by different geologists. 



Organic remains are extremely rare in these clays. The 

 writer has discovered sponge spicules, probably referable to 

 Hyalonema or an allied genus, and which are figured. The 

 following diatoms were also found: ISTavicula Grruendleri 

 A. iS. ; IsTavicula permagna, Edw. (fragments) ; M e 1 o - 

 sira granulata (Ehr.) Ralfs; IsTitzshia granulata 

 Grun., all fresh water species. At Croton landing a number of 

 impressions were found in the blue clay and on being submitted 

 to Prof. Hall were pronounced to be worm tracks. Mather in his 

 report^ mentions the finding of leaves in the clay beds back of the 

 medical college at Albany, and states that they resemble those of 

 an aquatic plant. 



Clays of the Champlain valley^ 



The clays of the Champlain valley are estuary formations of 

 the same age as the Hudson river clays. They underlie terraces 

 along the lake which have been elevated to a hight of 393 feet 

 above sea level. These terraces may be traced almost continu- 

 ously from Whitehall, at the head of Lake Champlain, to the 

 northern end of the lake and beyond it, but on account of the 

 extensive erosion which has taken place they are usually narrow, 

 and it is only at sheltered points like Port Kent and Beauport 

 that they become specially prominent. The section involved is 



1 Mather. Geol. New York, 1st dist. 1842. p. 123. 



2 Compiled largely from Emmons's Report geol. N. Y., 2 d dist. 



