518 F. G. CLA PP GLACIAL PEKIOD IN NEW ENGLAND 



to those found in the Gardiner clay indicates that they were scooped np 

 with their clayey matrix from a deposit of Gardiner clay wliich in pre- 

 Montauk time was more extensive in Boston harbor than at present. In 

 a few cases masses of Gardiner clay several inches in size have been found 

 incorporated in tlie dnimlins. 



Evidence afforded by fossils. — At the beginning of this investigation 

 it was not supposed that fossils would afford any evidence for correlation 

 or distinction between formations within the New England Pleistocene. 

 In order to get together all classes of material which might be of value, 

 however, the. various papers referring to the Pleistocene geology of this 

 part of New England were consulted and the lists of fossils tabulated. 

 To bring the names of the species up to date, the lists Avere referred to 

 Doctor W. H. Dall, of the IT. S. Geological Survey, with the request that 

 he correct the names of the species in cases M'here tlie usage lias changed 

 since the time the respective papers Avere published. The writer is in- 

 debted to Doctor Dall for making the corrections and putting the spe- 

 cific names in such form that the lists coiild be revised and the sjiecies 

 arranged in alphabetical order in the table. The writer alone is res])on- 

 sible, however, for the arrangement and the attempts at correlation. The 

 table is on pages 520-523. 



When tlie table was completed there was seen to be a striking contrast 

 between the first six columns and the other columns in species enumer- 

 ated. Of the 20 species found in and near Boston harbor (columns 

 2-6), (mly 8 were found to occur north of Winthrop. Of these 8, only 

 2, namely, Mya arenaria and Mytilus edulis, are found in more than one 

 locality elsewhere, and these 2 are found in 9 and 7 other localities 

 respectively. 



A still greater contrast is fotind between the species from Lynn, Dan- 

 vers, and Gloucester, Massachusetts, and those from Boston liarl)or. Of 

 the IT species from those three localities, within 10 to 20 miles north of 

 Boston, not a single species is foimd in any of the Boston Harbor local- 

 ities. Two of the species enumerated in the table, namely, Vencricardia 

 horeaUs and Venus mercenaria, are found in all five of the Boston locali- 

 ties, but are not found elsewhere. 



In order to compare the conditions south of Boston with this discrep- 

 ancy, the species from the Gardiner clay on Gardiners island, New York 

 (column 1), were compared with those at Boston. Of the 8 species 

 enumerated from Gardiners island, 4 were foimd near Boston, and only 2, 

 Chrysodomus deccmcostatus and Thraeia conradi. occur north of Boston. 

 These are found only at Portland and Biddeford respectively. 



