Thinnfeldia Leaf-Bed of Roseberry Topping. 9g 
For the present I wish more especially to draw attention to 
the beautiful manner in which these leaves are preserved. As 
will be seen from specimens which have been mounted on paper, 
the tissue of the original leaf is still fairly strong, and the 
individual leaves can be readily separated from the matrix and 
handled almost as easily as dried herbarium specimens. In 
this respect they differ from almost all other fossil plants, 
which occur either as impressions on a matrix, or as a coaly 
layer irremovably attached to the stone, or in exceptional 
cases impregnated with calcium carbonate or some other 
Vy y 
— 
Photo of Leaves of Thinnfeldia rhomboidalis detached from rock. Natural size. 
mineral substance. But here we have the plant itself, which 
has undergone comparatively little mineralisation, holding 
together by the strength of its own original tissues, a true 
example from the ‘ Herbarium Diluvianum.’ 
We may best speak of this kind of preservation as mummi- 
fication, for neither decay of the tissues nor replacement has 
gone on, only the gradual alteration of the less resistent sub- 
stances composing the original leaf. The chief reason why the 
Thinnfeldia leaves have retained their form so perfectly is that 
they possessed, when alive, a very thick and leathery cuticle, or 
outer layer to the epidermal cells, and the substance composing 
1915 Jan, }. 
