302 THE POTOMAC OK YOUNGER MESOZOIC FLOEA. 



not divide the leaves exactly in half; miduerve stout, rigid, and rounded; 

 lateral primary nerves very slender, not fully disclosed, going off at small 

 intervals from the midrib at an angle of about 45°, arching slightly forward 

 to near the margin, and then abruptly bending forwards to connect with the 

 next primary at its sudden bend, the connecting nerves forming a marginal 

 one ; ultimate reticulation not made out. 



Localities : Deep Bottom ; 72d mile-post, near Brooke ; not very rare 

 at the latter place. 



SALICIPHYLLUM, gen. nov. 



I group under this head a number of leaves imperfectly preserved and 

 of doubtful affinity owing to the poor preservation of the nerves. In the 

 nervation, so far as it could be made out, and in the shape of the leaves, 

 they appear to be nearer Salix than any other genus. The leaves may be 

 described as elongate-elliptical in outline, with midnerves strong at base 

 and much attenuated towards the summit ; lateral nerves slender, the pri- 

 maries going off very obliquely and curving strongly towards the summit 

 of the leaf, continuing approximately parallel with the margin, but grad- 

 ually approaching it. 



This genus has furnished a considerable element to the Potomac flora, 

 the plants being chiefly found in the strata showing the flora with more 

 recent aspects. 



Saliciphvllum longifolium, sp. nov. 



Plate CL, Fig. 12. 



Leaves small, oblong elliptical, very long in proportion to their Avidth, 

 summit not seen, gradually narrowed towards the base ; midnerve towards 

 the base very strong, attenuated above ; lateral nerves slender ; primary 

 nerves going off at an acute angle, inclining forward to near the margin, 

 then abruptly bent forward to form an arch which is approximately parallel 

 with the margin, this connecting with the next primary above at the point 

 where it suddenly bends ; the successive arches make a continuous sinuous 

 marginal nerve, which is as strong as the primaries connected by it ; inter- 

 calated subordinate nerves from the midrib send off branches which unite 



