738 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



whitish clay, abundantly pierced by the vertical pipestem concretions, es]ie- 

 cially in its upper portion, where it grades into e, a thick stratum of loess, 

 which is 10 feet thick over all the lower plain, and still thicker where it 

 projects downward to till the old river beds. It rises up the terrace scarp 

 with a thickness of 3 feet, and is continuous over the upper plain with a 

 thickness of 6 feet. This represents the accumulated deposits of the Con- 

 necticut in flood time, laid down since Fort River abandoned its bed at 

 d and d'. This stream now runs inniiediately adjacent, with its surface coin- 

 cident with that of the Connecticut. When it occupied this old oxbow it 

 flowed at a level 13 feet higher, and this represents certainly more than 

 half of the amount by which the Connecticut has lowered its bed in the 

 bottom of Hadley Lake since it shrunk to its present size. This would 

 assign to the fossils found here an age about intermediate between those 

 of the Champlain clays below and the present time, or somewhat nearer to 

 the present flora than to the older; and the habits of the fossils themselves 

 agree with this, and indicate a climate like that of northern Vermont or 

 Canada. It is interesting that a fragment of charcoal from some light, open- 

 grained wood was found in the midst of the matted leaves of the leaf bed 

 and was certainly of the same age with them. It was about as large as a 

 walnut. 



fossiijS of the terrace period. 



\tebtebbates. 



Mastodon americanus. — In 1872 Dr. Edward Hitchcock, jr., writes: "I 

 have seen and identified a mastodon's molar which was found in the town 

 of Coleraine, Massachusetts. It was shoveled out of a muck bed on the 

 tixrm of Elias Bardwell." ' The tooth is still in Mr. Bardwell's possession. 



MOLLUSKS. 



In digging in a marl pit which lias formed liy the filling of a small 

 pond on the surface of the till on the farm of Fred Conant, at East Shel- 

 burne, large quantities of white fresh-water shells are at times thrown out. 

 They are very well preserved, and consist of tlie following species: 



Lymnea elodes Say. — Length, 30 """. Common. 



Planorhis trivolvis Say. — Large diameter, 25 '"™; small diameter, IS""™. 

 Common. 



' Am. Jour. Sci., 3d series, Vol. Ill, p. 146. 



