514 Descriptions of the Fossil Plants 



nules oblong, obtuse, somewhat curved upward, vinited at 

 their bases, margins acutely denticulate, sometimes entire; 

 nervation strongly marked, secondary nerves mostly once- 

 forked, basal nerve of each pinnule on the lower side often 

 twice-forked. 



This elegant species seems to have grown in the greatest 

 abundance during the period of the deposition of the coal 

 of Vancouver's Island ; the shales over the Newcastle 

 coal being so closely packed with its fronds as to show 

 them crossing each other in every direction under every 

 lamina that is raised. From their very abundance and 

 consequent interference, it is impossible to obtain the en- 

 tire outline of a frond, or even of a pinna ; the frond must, 

 however, have been of considerable size, and the pinnse 

 eight or ten inches in length. These last are linear in out- 

 line, some of them somewhat curved, others quite straight, 

 the difference being doubtless due to their different posi- 

 tions in the frond. The pinnules are usually arched up- 

 ward, very broad at the base, rounded or obtusely pointed 

 at the summit. Where well preserved, the margins of the 

 larger ones are seen to be finely but distinctly denticulate. 

 The nervation is quite strong, but the frond was evidently 

 thick and firm, and though very prominent on the under 

 side, on the upper the nerves are scarcely visible. The 

 midrib is slightly sinuous, and vanishes toward the sum- 

 mit of the pinnule. The secondary nerves are generally 

 once-forked, but the upper ones are simple, and the lower 

 one on the lower side is often twice-forked, or rather two 

 once-forked nerves spring from the same base. 



Among fossil species this may be compared with A. 

 Filix antiqua Al. Br. Heer, (Flor. Tab. Hcivet. 1, S. 35, 

 Taf. XI. fig. 1,) but though crenulated, the pinnules in 

 that species are not denticulate, and they are not curved. 

 The nerves are also less strong and more simple than in 

 our plant. 



