40 ONYCHIOPSIS. 
on the general character of the fructification, and not on details 
of sporangial structure. Unfortunately no sporangia are sufficiently 
clearly preserved to afford that important assistance which a 
more intimate knowledge of them would give. It is to be 
regretted that the material from the English Wealden does not 
often enable us to learn anything as to histological structure. 
There is, however, a notable exception in Tempskya Schimpert, 
Corda, in which structural details have often been more or less 
clearly mineralized, thus enabling us to add something towards the 
elucidation of the real botanical position of this remarkable fossil. 
A. Genera assigned to existing Families. 
Order LEPTOSPORANGIAT A. 
The Sporangia, with walls composed of a single layer of cells, 
are developed from single surface cells. 
Family POLYPODIACEZ. 
Sporangia stalked, and with a vertical incomplete annulus. 
Genus ONYCHIOPSIS, Yokoyama. 
[Journ. Coll. Sci. Japan, vol. iii. 1890, p. 26.] 
Frond tripinnate, main rachis slender, may be winged, pinne 
alternate, approximate, lanceolate. Pinnules narrow, lanceolate, 
acute, alternate, the larger ones serrate, and gradually passing into 
pinnules with narrow ultimate segments. Fertile pinne with 
alternate elliptical pinnules which differ in shape from the sterile 
pinnules, and have the sporangia on the lower surface, giving them 
the appearance of raised elliptical bodies. 
This genus was instituted by Yokoyama for the reception of 
a Japanese species, originally described by Geyler’ as Thyrsopteris 
elongata, and afterwards referred to by Yokoyama as Dicksonia 
elongata. The occurrence of fertile pinnules of a distinct and 
unusual type led to the removal of the specimens from Thyrsopteris 
to Onychiopsis. Yokoyama pointed out the resemblance between 
the fertile pinnse of the Japanese specimens and those of the 
1 Palwontographica, vol. xxiv. 1876-77, p. 224, pl. xxxi. fig. 4. 
