DESCKIPTION OF THE SPECIES. 157 



I'l. LXl, Fi^'. 4, dirters IVom tlie typical lonns in liavinj^- the termiiuition of 

 the pinnules an oblong lobe, which is slightly notched or toothed. Figure 

 f) of the same plate appears to be the summit of an ultimate pinna, dift'eriui;- 

 in the trilobate terminal pinnule from tlie normal termination, as sliown in 

 PI. LXIII, Fig. 1, where the lobes gradually diminish in size towards the 

 summit. 



CteNOPTERIS VIRGINIENSIS, sp. nOV. 

 Platl^ LXII, Pis;. 4 ; l>latc LXV, Pij;. 1 ; Plate LXVI, Pig. 4. 



Frond bipinnate or tripinnate, probably arborescent ; rachises stout, 

 strongly ridged or keeled; ultimate pinnaj subopposite; leaf-substance 

 thick ; pinnules comparatively short and broad in proportion to their 

 length, opposite or alternate, slightly decurrent, distinct to the base or 

 slightly united, attached by the entire base, rounded obliquely on the 

 upper side at base, sliglitly curved forwards, posterior margin nearly 

 always free from teeth, terminating in a triangular tooth, with an acute 

 tooth on each side of this at the summit of the pinnule, and with an acute 

 or spinous tooth about midway on the anterior margin ; nerves proceeding 

 from a common point on the rachis of the ultimate pinncC, branching sev- 

 eral times and diverging slightly, the ultimate branches long and nearly 

 parallel. 



Locality: Fredericksburg; rather rare. 



This plant has a very stout principal rachis, but the species is decid- 

 edly smaller than C. im'igms, and shows some important points of differ- 

 ence from it. On nearly all the pinnules there are no teeth on the poste- 

 rior margin of the pinnules, and only one on the anterior margin. The 

 most important difference is in the nerves. They form two principal 

 nerve-bundles, which depart from a common point and not from the entire 

 base of the pinnule. Thus they show a tendency to form a niidnerve witli- 

 out actually developing one. In this feature there is an approach to the 



Sdcropteria type. 



Ctenopteris .minor, sp. nov. 



Plate LXVII, Fig. 3. 



Fronds small, arborescent, bipinnate or tripinnate ; principal rachis 

 strong, rigid ; ultimate pinuix? with rachises strong towards the base and 



