412 EXPLANATION OF PLATES I. AND II. 



there, and the nervation differs from that of the mulberry 

 in that part, in two or sometimes three veins of smaller 

 size originating also from the mid-rib or footstalk to supply 

 the base of the leaf. Five, or sometimes six veins may, 

 therefore, be said to spring from the top of the footstalk, 

 the lower ones being secondary as to size. In the leaf 

 of the mulberry, these smaller basal veins are branches of 

 the lateral veins. No entire impression exists. The largest 

 fragment must have belonged to a leaf between seven and 

 eight inches long. The general outline seems to have 

 been cordate, with the lobes at the base full and perhaps 

 overlapping, and the apex acute, but not acuminate as 

 in the mulberry. The margin is serrato-dentate above, 

 and simply undulated, or nearly even, at the base. The 

 teeth are generally semi-ovate with a little point, or mam- 

 millate as in the mulberry, but are not so closely set. They 

 are somewhat unequal in size, and occasionally denticulate, 

 a larger tooth being notched by a single smaller one. In 

 some specimens the sinuses between the teeth are acute, 

 but more generally they are obtuse. This is one of the 

 most common leaves in the deposit, and one impression of 

 it often succeeds another in layers thinner than common 

 writing paper, and so blended together at the margins of 

 the leaves that the impressions cannot be obtained perfect. 

 Fig. 1. Plate I. is intended to represent a small frag- 

 ment of this leaf, drawn of the natural size, but the dis- 

 tinction between the secondary transverse veins and their 

 minor ramifications has not been maintained in the figure 

 as to size, nor are the ultimate veins shown. The teeth 

 are more obtuse in the side of the cast which has been 

 drawn than they appear in the layer which Avas removed 

 from it, owing to the way in which the matrix has adhered 

 at that part ; but it would appear that some of the leaves 

 varied in having more obtuse teeth, if we may judge from 

 two other casts very similar to this one in all other respects. 

 Upwards of an inch of petiole remains in some of the spe- 

 cimens. 



