232 DR. A. C. SEWARD: 
large fronds of Camptopteris spiralis described by Nathorst are from the 
rich Rhætic strata in Scania. 
Dictyophyllum would seem to have attained its maximum development, as 
measured by size of frond and range of form, in the Rhætic period : this 
is clearly shown by the wonderful specimens figured by Zeiller and Pelourde 
from Tonkin and by Nathorst from Southern Sweden. The genus was also 
well represented in the Rhætic flora of Franconia. The line between 
Rheetic and Jurassic floras cannot readily be drawn. For present, purposes 
“the floras of the localities enumerated may be classed together: Dictyo- 
phyllum and Thaumatopteris are practically absent from Rheetic-Jurassic 
floras in North America, but Dietyophyllum is recorded from Alaska. 
Dietyophyllum, sometimes also Thaumatopteris, occurs in many localities in 
Europe, from England to Poland, Sardinia, and Russia, in Scania and the 
Island of Bornholm; in Chile and the Argentine, China and Japan, Queens- 
land and New Zealand; also in Graham Land on the edge of Antarctica ; 
in Persia and Afghanistan. Nathorst speaks of thousands of fronds of 
Dictyophyllum in the plant-beds of Southern Sweden, and sees in the 
diversity of leaf-form evidence of a centre of development. It is remark- 
able that the two regions of greatest development of this type of fern would 
seem to have been Tonkin and Scania, though it may be that the greater 
richness of the Rhætic flora in these two areas is due to conditions unusually 
favourable for fossilisation. 
Clathropteris. The genus is represented in the Upper Triassic flora of 
Lunz and by very large fronds in beds assigned to the same horizon in 
Virginia. It occurs in Rhætie beds in Scania, Russia, Tonkin, and China ; 
also in Jurassic strata in several European lotalities. One imperfect speci- 
men referred with some doubt to this genus was found in rocks in Egypt 
which may be Cretaceous in age. 
Hausmannia. This, the genus nearest to Dipteris, is represented by some 
imperfect specimens in the Rhætie beds of Scania ; by several well-preserved 
fronds in the Rheetic-Liassic strata in Bornholm ; also in Liassic beds in 
Austria, An imperfect specimen from Jurassic strata in Alaska has been 
referred to Hausmannia. The genus is widely spread in Upper Jurassic, 
Wealden, and Lower Cretaceous rocks in England, the North-East of 
Scotland, Belgium, and France, and is especially abundant in Lower 
Cretaceous beds at Quedlinburg in Germany. Hausmannia is probably a 
later offshoot from the parent stock than the genera of the Camptopteridine. 
Laccopteris is represented by well-preserved fertile specimens in the 
Rheetic floras of France and Franconia. The oldest are from the Upper 
Triassic beds of Lunz. It is characteristic of Jurassic floras in Europe and 
is recorded from Cretaceous rocks in Western Greenland. 
Matonidium occurs in several Middle Jurassic floras, in Wealden beds in 
England, Belgium, Germany, Russia, and other countries, and a species 
