the leaflets are imbedded in a scattered manner, — the whole mine- 

 ralized by chalcedony. The distinctions of the supposed species 

 depend mainly upon the comparative size of the leaf-stalks, and the 

 form which they exhibit in a transverse section. 



1 1 . Rhachiopterides. — This is avowedly an artificial group founded 

 merely on fragments of the leaf-stalks of Ferns, which have been 

 found so preserved as to allow of the examination of their internal 

 structure; but with no leaves attached to them. M. Corda thinks 

 it expedient to distribute these remains among six different genera, 

 which he groups according to the number and form of the vascular 

 bundles in each leaf-stalk, thus : — 



A. With one vascular bundle, which is curved upwards or inwards. 



I. Selenopteris. Two species : — S. Radnitzensis and S. involuta. 

 The vessels of the first species are of the porous structure (an un- 

 usual circumstance in Ferns), in the second they are scalariform. 



II. Gyropteris. One species ; — G. crassa, 



B. With one vascular bundle, which is revolute. 



III. Anachoropteris. Two species: — A.pulchra and A. rotun- 

 data. The genus is remarkable in two respects — that its vascular 

 tissue- consists of porous vessels, and that the bundle formed of these 

 vessels is rolled back, or presents its concavity towards the back of 

 the leaf-stalk, which Corda observes is not the case in any recent 

 Fern that he has been able to examine. 



C. With two or more vascular bundles. 



IV. Ptilorhachis. One species : — P, duhia, 



V. Diplcyphacelus. One species : — D. arboreus. 



VI. Calopteris. One species: — C. dubia. This, like all the other 

 remains included by Corda under the present tribe, occurs in the 

 coal-formation at Radnitz in Bohemia. 



12. GleicheniacecB,— Five different genera of fossil Ferns had been 

 enumerated by Presl as belonging to this tribe, namely: — Laccopteris, 

 Asterotheca"^, Phialopteris, Gutbieria and Partschia. To these 

 Corda adds two others, Hmolea and Chorionopteris. 



I. Hawlea. One species : — H, pulcherrima. Founded on a spe- 

 cimen in fructification obtained from the coal-formation of Bohemia. 

 It agrees very closely, in the form and arrangement of its fruit, 

 with the recent genus Mertensia (included in Gleichenia by Sir W. 

 Hooker), nor does there appear, so far as the evidence goes, to be 

 any sufficient reason for separating them. 



II. CJiorioTiopteris. One species: — C. glexchenioides^ found in 

 Sphserosiderite in the coal-formation of Radnitz. This is a plant 

 much more peculiar in its structure than the preceding, and mate- 

 rially different from auy of the recent Gleicheniaceae ; in fact, the 

 author considers it as intermediate between that tribe and the Cya- 



* Asterocarpus of Goeppert. 



