Impressions of fossil ferns and fern allies from the Pennsyl¬ 
vanian. Natural size. Figure i: A fern leaf (Sphenop- 
teris). Figure 2: A fern leaf (Neuropteris). Figure 3: 
A fern leaf (Pecopteris). Figure 4 : A branch of a horse¬ 
tail (Calamites). 
