OF LOWEll Gil KENS AND PLANTS. 3 



scattered, but generally in definite sori on the foliage leaves, 

 and generally on the lower surface. In some cases fertile leaves 

 are specialised to a greater or less extent, but they do not 

 form cones. 



Genus WEICHSELIA, Stiehler. 

 [Paloeontographica, vol. 5, 1857, pp. 73-75.] 



The genus is founded on the external impressions of fern- 

 foliage. 



Diagnosis. Fronds bi-pinnate or tri-pinnate * along a broad 

 and rigid rachis ; pinnae long, having strong axes which 

 make the pinnules appear relatively small. Pinnules entire, 

 alternate, attached separately by their whole bases ; apices 

 obtuse, varying somewhat in length but averaging 3-6 mm. 

 long, and in general, half that width ; margins of the pinnules 

 nearly parallel. \ r enation finely reticulate, of the LoncJiopteris 

 type, with a very strong, well-marked middle nerve. In most 

 specimens the mid-rib is all that remains of the veins, the fine 

 secondary reticulations being very rarely preserved. Fructifi- 

 cations in the form of sori are reported, but fertile specimens 

 are rare and not very distinctly preserved. 



Impressions, and particularly sandstone-casts of the foliage, 

 are common in Europe, numerous large fronds occurring in 

 Germany, llussia, England, and elsewhere. It is also reported 

 from Peru, and appears to be locally very common in South 

 Dakota (see Ward, 1899). It is principally characteristic of the 

 Neocomian as a whole, and is a typical " Wealden " plant, but 

 is found as high as the Gault, though infrequently. 



Judged simply by its external morphology, there seems no 

 conclusive reason why Weichsdia should not be included in the 

 form-genus Lonchopteris, but it is customary to restrict the 

 latter name to the forms from the older deposits, and retain 

 Stiehler's generic name for the later forms, though he founded 

 it in ignorance of the fact that the frond had reticulated veins 

 like Lonchopteris. 



The published figures of the venation are inadequate, even 

 in the recent papers on the subject, and reference should be 



* See Zeiller, 1910. 



