8 Thinnfeldia Leaf-Bed of Roseberry Topping. 
Grey clay ; ” ™ ie 6 inches. 
Black coaly clay : 4 inches. 
Grey yellow clay passing into Upper Liassic shales. 
This gradual passage of the Liassic into the Lower Estuarine 
is of some interest, more especially when we remember that 
Thinnfeldia rhomboidalis is typically a Liassic plant. I do 
not think it is possible to say definitely, as the result of exami- 
nation of the strata, whether the beds which we are discussing 
should be reckoned as of Liassic or Lower Estuarine Age. 
The leaves are compound pinnate structures of various 
sizes (see fig.), sometimes reaching about a foot in length, but 
it is seldom that complete leaves are seen or can be extracted 
owing to their constant overlapping. It may, perhaps, be 
more correct to speak of them as fronds consisting of a central 
stalk or rachis some 2-4 millimetres wide, bearing ovoid or 
lanceolate pinna on either side. The shape of the pinna or 
leaflets is somewhat varied, depending to some extent on their 
distance from the apex or the base of the frond, and it varies 
also in different fronds, but in all cases the apex is bluntly 
rounded, the base is decurrent on the lower side and truncated 
on the upper side. Im some cases the pinnae are so close 
together as to overlap one another, but in other specimens they 
may be 3-4 millimetres apart ; towards the base of the frond 
they appear to be inserted on the upper side of the rachis 
somewhat as in the fronds of some Cycads and Bennettitaleans. 
At the lower end, the rachis may extend for 6 centimetres or 
more below the lowest pinnae, it shows longitudinal ridges, 
and some transverse wrinkling in the centre. In the centre 
of each pinnae is a strong midrib which is almost always very 
conspicuous ; the secondary veins are, however, very indis- 
tinct, and though they frequently appear plain when the 
specimens are first collected, they are later almost indistinguish- 
able. There were, however, fine veins given off at an acute 
angle to the midrib, and forking once or twice on their way to 
the margin. 
At the apex of the frond, the pinnae decrease somewhat 
irregularly in size and they become confluent, the tip being 
occupied by a terminal leaflet. Near the apex the distinction 
between pinnae or leaflets and stalk seems to be lost. 
Pinnae are frequently irregularly lobed or possess small 
notches on their margins. The very great variation in shape 
suggests that several species of Thinnfeldia based almost 
entirely on small differences in outline ought to be dropped, for 
Thinnfeldia rhomboidalis certainly shows very different forms.* 
* A very good review of the state of knowledge of the genus has just 
been published by Antevs. K. Svenska. Vet. Akad. Hand.,Bd. 51, No. 
6, 1914. 
Naturalist, 
