FLORA OF- THE OOLITIC EPOCH. 749 



96 Ferns, 61 Cycads, and 14 Conifers. The distinctive characters of 

 this flora are, the rarity of Terns with reticulated venation, which 

 are so numerous in the Lias, the frequency of the Oycadaceous genera 

 .Otozamites and Zamites, which are most analogous to those now 

 existing ; of a "remarkable group presenting very anomalous structure 

 in their organs of reproduction, to which Mr. Carruthers has given 

 the name of WiUiamsonia, and the diminution of Ctenis, Ptero- 

 phyllum, and NUssonia, genera far removed from the living kinds ; 

 and lastly, the 'greater frequency of the coniferous genera, Brachy- 

 phyllum (fig. 931), and Thuites, which are much more rare- in the 

 Lias. In the Scottish Oolite at Helmsdale Miller has detected about 

 60 species of plants, including Oycadacese and Coniferse, with detached 

 cones, and Fern forms resembling Scolopendrium. He also discovered 

 a species of Equisetum (fig. 932), and a Calamite which is a connect- 

 ing link between the Oolitic and Carboniferous epochs. 



There is an absence of true coal-fields in the secondary formations 

 generally ; but in some of the Oolitic series, as in the lower Oolite at 

 Brora, in Sutherlandshire, and the Kimmeridge clay of the upper 

 Oolite, near Weymouth, there are considerable deposits of carbon- 

 aceous matter, but the vegetable remains are only in the state of im- 

 perfect lignite ; some suppose that the Brora coal was formed chiefly 

 by Calamites columnaris. In the sandstones and shales of the Oolitic 

 series, especially in the lower Oolite of the north of England, as at 

 Whitby and Scarborough, as well as in Stonesfield slate, the Portland 

 Crag of the middle, and the Portland beds of the upper Oolite, nume- 



Fig. 934. 



rous fossil plants are found. Peuce Lindleyana is one of the Coniferse 

 of the lower Oolite. Beania is a Cycadaceous fossil from the Oolite 

 of Yorkshire. Araucarites sphserocarpus is found in the inferior Oolite. 

 The upper Oolite at Portland contains an interesting bed, about a foot 

 in thickness, of a dark brown substance, containing much earthy 



Fig. 933. Tlie Dirt-bed of tlie island of Portland, containing stumps of fossil CycadaoeEe in 

 an erect position. Fig. 934. Cycadoidea megalophylla (Mantellia nidiformis of Brongniart), 

 a subglobose depressed trunk, with a concave apex, and with the remains of the petioles 

 disposed in a spiral manner, the markings being transversely elliptical. It is found in the 

 Oolite of the Island of Portland, in a sUicifled state. 



