314 THE STRUCTURE AND SUCCESSION AT 



building stone, a considerable quantity of which has been 

 quarried for local use. It is rich in fossils of the genera 

 Sigillaria and Lepidodendron. Here, too, I found a cast of the 

 pith of a Calamodendron. It very much resembles the stem of 

 Calamites, but is distinguished by the absence of leaf-scars. 

 The Calamodendron, as now found fossil, appears to be the pith 

 of a stem which had a thick bark and woody coating. 

 This pith doubtless decayed tirst, and the hollow stem filled 

 with sand or cla3^ Later the outer part disappeared, leaving 

 a stone cast of the interior. Although this quarry stone con- 

 tains numerous fossils, very few remain distinct enough to 

 determine their species. Sigillaria trunks are found varjang 

 from two to eighteen inches in diameter. 



Nearly all the coal seams have clay or shale above them. 

 One, however, the last but two before Lloyd's Cove seam, is 

 overlain by very coarse, gritty micaceous sandstone. Condi- 

 tions succeeding the formation of this coal must have been 

 somewhat different from those succeeding previous beds. The 

 ordinary fine clay and shale usually overlying the vegetable 

 matter came from the gentle filling up of swamps with fine 

 material during a period of slow gradual subsidence. The coarse 

 sandstone on the other hand, must have been deposited in 

 moving shallow water near shore. This may very likely have 

 come about by a sudden but comparatively slight subsidence 

 after the prolonged interval of rest during which the coal had 

 accumulated. For, if depression had not been sudden, the \vater 

 would not have attained sufficient depth to produce waves capa- 

 ble of moving and spreading out the coarse sand without any 

 intervening layer of day. Nor could the depression have been 

 very great, for then the water would be so deep that coarse 

 sand could not be carried out any distance over the sea-floor. 

 A second possibility is the influx of sand from the action of 

 storms breaking over the low bars into the lagoon behind. In 

 this sandstone, false-bedding is extremely common, but with 

 no particular current direction. Its presence indicates the 



