76 THE POST-PLIOCENE PERIOD. 



In some specimens sent to me by Mr Matthew, I find, in addition 

 to the forms above enumerated, some microscopic organisms, more 

 especially Polystomella striatopunctata [umbilicata of Walker), and 

 several species of Cythere ; and among the Bryozoa I recognise Pustu- 

 lipora, Tubulipora serpens and Crista eburnea, all in small fragments. 



In the absence of fossils, the drift of Nova Scotia contrasts strongly 

 with the Post-pliocene clays and sands of the lower St Lawrence and 

 the St John. These deposits abound in marine shells, and mark the 

 stages of recession of the sea as the American land rose from the 

 great depression of the period of the boulder formation, in which 

 nearly the whole continent was submerged. The absence of the fossil- 

 iferous marine clays in Nova Scotia may indicate a more rapid elevation 

 of the land, not giving time for permanent sea-bottoms ; or, on the 

 other hand, a slow rise accompanied by very great denudation. The 

 position of Nova Scotia and the aspect of its boulder clay point rather 

 to the latter conclusion. In this case, remnants may exist ; and, 

 judging from appearances in Canada, Maine, and New Brunswick, I 

 should suppose that marine remains are most likely to be found at the 

 junction of the boulder clay with the overlying stratified drift, and 

 in places sheltered by hills or ledges of rock. From papers on this 

 subject, relating more especially to Canada, I may select the following 

 statements as important to the geology of these formations in Acadia 

 as well : — * 



The arrangement of the Post-pliocene deposits at Logan's Farm 

 near Montreal, and Beauport near Quebec, confirms the subdivision, 

 which I have attempted to establish, of these beds into an underlying 

 unstratified boulder clay, a deep-water bed of clay or sand (the 

 " Leda clay " of Montreal), and, overlying shallow-water sands and 

 gravels (the " Saxicava sand"). This arrangement shows a gradual 

 upheaval of the land from its state of depression in the boulder clay 

 period, corresponding with what has been deduced from similar 

 appearances in the Old World. " The upheaval of the bed of the 

 glacial sea," says Forbes, " was not sudden but gradual. The phe- 

 nomena so well described by Professor Forchammer in his essays on 

 the Danish drift, indicating the conversion of a muddy sea of some 

 depth into one choked up with sand-banks, are, though not universal, 

 equally evident in the British Isles, especially in Ireland and the Isle 

 of Man."f 



We now have in all, exclusive of doubtful forms, about one hun- 

 dred species of marine invertebrates from the Post-pliocene clays of 

 the St Lawrence valley. All, except four or five species belonging 



* Canadian Naturalist and Geologist, vols, ii., iii., and iv. 

 f Memoirs of Geological Survey. 



