318 Laliee — Late Paleozoic Glaciation . 



underlying' Aftonian stratified drift, as figured by Chamberlin and 

 Salisbury.* 



(2) Scarcity of striated pebbles and bowlders in the tillite has 

 been compared by Mr. Sayles to the similar case in the Pleistocene 

 of southern Rhode Island. Last summer (1913), in company with 

 Dr. A. Knopf of the U. S. Geological Survey, I had an oppor- 

 tunity of examining a number of well-defined lateral and frontal 

 moraines which were built by the Pleistocene valley glaciers of 

 the Sierra Nevada in California. We were much impressed by 

 the great scai'city of striated rock fragments in these moraines. 

 In the Boston Basin this feature may be coordinated with the 

 fact that here ice seems to have travelled over unconsolidated 

 sediments instead of over a hard rock floor. 



(3) The large angular blocks of slate and shale included in the 

 tillitef resemble the masses of Aftonian gravel inclosed in the 

 Kansan till, as figured by Chamberlin and Salisbury.;}; 



(4) Mr. Sayles observes that near the top of the tillite, "inter- 

 calated stratified beds may be found." I have frequently noted 

 similar beds of sand, some contorted and some not so, in the 

 Pleistocene till of the Boston Basin, both in irregular till sheets 

 (ground moraine) and in drumlins. 



(5) Contemporaneous deformation was observed last autumn 

 in Pleistocene sand deposits at Woodland, Mass.§ 



(6) The presence of isolated pebbles and bowlders was reported 

 in the Cambridge brick clays which are of Pleistocene age.| 



(7) The Somerville slates, at the base of which are found evi- 

 dences for glacial action, are remarkable for the absence of fossils. 

 It is interesting to note the similar absence of fossils in the Pleisto- 

 cene brick clays of Cambridge and other localities.^ 



* Geology, vol. iii, p. 385. 1906. 

 f Sayles, op. cit., pp. 143, 149. 

 | Geology, iii, p. 386. 

 §Lahee, F. H., op. cit. 



IJShaler, N. S., Woodworth, J. B., and Marbut, C. F., U. S. G. S., Ann. 

 Kept., 17, Pt. 1, pp. 970 and 990. 



TfShaler, N. S., etc., op. cit., pp. 993-994. 



Massachusetts Institute of Technology, February 10, 1914. 



