

lO^*"- It. K 'Dodge — Pletsiochie Fossils from Mass. 



more conspicuously in the clays of the drnmlins of Boston 

 Harbor than in any of the inland drumlins 1 have had an 

 opportunity to note in Western Massachusetts and Connecti- 

 cut. The possible presence of such a large amount of previ- 

 ously eroded material in the deposits laid down during the 

 last stages of the ice age relieves us from considering that a 

 moving continental ice sheet is such a great erosive agent as 

 we are wont to believe it. 



Mr. W. O. Crosby,* believes that " possibly as much as one- 

 fourth and quite certainly not more than one-third of the de- 

 tritus composing the till of the Boston basin was in existence 

 before the ice age, and that the remaining two-thirds or three- 

 fourths must be attributed to the mechanical action of the ice- 

 sheet and its accompanying torrents of water." Comparing 

 this estimate of the amount of erosion by the ice sheet in 

 Boston Harbor with the scant amount of work done by the 

 ice sheet in Western Massachusetts and Connecticut, as shown 

 by the very conspicuous bed rock topography formed in pre- 

 glacial times and but little affected by the ice advance, the 

 estimate seems to be very large indeed. 



The most interesting problem suggested by the presence in 

 our drift of such fossil fragments as I have described is, how- 

 ever, that of the relative positions of land and sea in the dif- 

 ferent epochs of pleistocene times. For that reason, even the 

 evidence of one small fragment like that of Scaphqrca trans- 

 versa is important, though it gives us but one small bit of 

 proof of the warmer waters in Massachusetts Bay in the times 

 immediately previous to the last ice age. It only remains in 

 conclusion to say that similar assemblages of pleistocene shells 

 have been found in our glacial drift in other localities, but 

 mainly on the southern shores of New England. The most 

 important discoveries have been those of Desorf and Verrill 

 and Smith:}; from the apparently interglacial beds of Sankaty 

 Head, Nantucket. At this locality more than a score of spe- 

 cies have been found, occurring in two distinct beds. The 

 lower beds contain warm water forms and the upper mostly 

 worn fragments of northern forms. On our northern shores 

 no section so rich in pleistocene fossils has as yet been found 

 as that of Winthrop Great Head, although similar deposits 

 have been found by Prof. Shaler at Gloucester, Mass., and by 

 others at different localities on the coast of Maine. The reason 

 for the occurrence of so many different species of fossils in 

 this one clrumlin in Winthrop, situated as it is among so many 

 neighboring unfossiliferous drumlins, still remains a mystery. 



Harvard University, Cambridge, Mass. 



*Proc. Bost. Soc. Nat. Hist, vol xsv, p. 115-140. 

 f Quar. Jcur Geol. Soc. Lond . vol v, pp. 340-344. 

 % This Journal, III. vol. x, 1875, pp. 364-370. 



