414 EXPLANATION OF PLATES I. AND II. 



as only the lower half of the cast remains. About an inch 

 and a half of broad footstalk is met very acutely by the 

 cordate base of the lamina. The margin is cut by rather 

 large and somewhat remote acute serratures, the first of 

 which is about three quarters of an inch from the foot- 

 stalk. The under side of each tooth of the serrature slopes 

 gradually down to meet the much shorter upper side of 

 the next tooth, which stands out horizontally. Each tooth 

 is traversed by a vein of the third order, which ends in the 

 acute point. From the fragments we may estimate the 

 length of this leaf at five inches, and the breadth at three. 

 I forbear describing other fragments, which probably 

 represent the upper end of this leaf, as there are some 

 differences in the surfaces of the casts. 



No. 12. 



A very sharp cast occurs among the others of the upper 

 part of a leaf, which in the acuteness of the veins and their 

 form resembles Tilia euro-pea, while in its general outline 

 and rugose surface (but not in its margin) it is similar to 

 some of the lower leaves of Corylus avellana. The veins 

 meet the mid-rib in pairs, or alternately ; the lower ones 

 are nearly straight, the upper pairs are segments of a cor- 

 date curve, concave upwards. The veins of the next order 

 pass directly between the branches in a straight line, or 

 with a few anastomoses, and the ultimate reticulations are 

 minute. The lamina is prominent above, from the tight- 

 ness of the principal and secondary veins, and the cast of 

 the upper surface shows also the prominence of the minute 

 netting, corresponding of course to furrows in the original 

 leaf, so close as to give it a somewhat woolly appearance 

 to the naked eye. The cast of the under surface is convex 

 where that of the upper one is hollow, shows the ultimate 

 ramifications of the veins less distinctly, and is irregularly 

 dotted by punctures visible by aid of a lens, and which 

 probably had their origin in a stiff and scattered pubes- 



