166 



THE GEOLOGICAL HISTORY OF PLANTS. 



mind that they are usually the marks of cones ; and the great size of 

 the cones of Lepidophloios accords with this conclusion. 



The species of Lepidophloios are numerous, and individuals are 

 quite abundant in the coal formation, especially toward its upper 

 part. Their flattened bark is frequent in the coal-beds and their 

 roofs, affording a thin layer of pure coal, which sometimes shows the 

 peculiar laminated or scaly character of the bark when other charac- 

 ters are almost entirely obliterated. The leaves also are nearly as 

 abundant as those of Sigillaria in the coal-shales. They can readily 

 be distinguished by their strong, angular mid-rib. 



The markings of Lepidophloios may easily be mistaken for those 

 of the Clathraria type of Sigillaria. When the stem only is seen, 

 they can be distinguished by the length of the leaf- bases in Lepi- 

 dophloios, and by the dominant central vascular scar ; also by the 

 one-nerved and ribbed leaves. Where the large, round marks of the 

 cones are present, these are an infallible guide, never being present 

 in Sigillaria. As the cones grew on the upper sides of the branches, 

 the impression of the lower side often shows no cone-scars, or only 

 two lateral rows, whereas on the upper side of the same branch they 

 appear spirally arranged. I may describe as an example — 



Lepidophloios Acadianus, Dawson. Leaf-bases broadly rhom- 

 bic, or in old stems regularly rhombic, prominent, ascending, termi- 

 nated by very broad rhombic scars having a central point and two 

 lateral obscure points. Outer bark laminated or scaly. Surface of 

 inner bark with single points or depressions. Leaves long, linear, 

 with a strong keel on one side, five inches or more in length. Cone- 

 scars sparsely scattered on thick branches, either in two rows or 

 spirally, both modes being sometimes seen on the same branch. 

 Scalariform axis scarcely an inch in diameter in a stem five inches 

 thick. Fruit, an ovate strobile with numerous acute scales covering 

 small globular spore-cases. This species is closely allied to TJloden- 

 dron majus and Lepidophloios laricinus, and presents numerous 

 varieties of marking. Coal-formation, Nova Scotia. 



Family Calamite je ; Genus Cal amites, Suckow. 



The plants of this genus are unquestionably allied to the mod- 

 ern Equisetaceai, but excel these so much in variety of form and 

 structure, and are so capricious in their states of preservation, and so 

 liable to be mistaken for parts of plants generically different, that 

 they have given rise to much controversy. The following considera- 

 tions will enable us to arrive at some certainty. 



The genus Calamites was originally founded in the longitu- 



