DESCRIPTION OF TIIH SPECIES. 177 



Zitteli (Glossnzainitcs Zittd'i Scluni[)cr),' l)nt tlie leaflets are not so obtuse and 

 are farther apart, whilt; the nerves are more branched. 



CTENI8 (Lindley and Ilutton), Zigno emend.'- 



Leaf profoiiiullv piiinatitid; rachis thick, striated, and furrowed; leaf- 

 lets or lacini;« approximate, linear-elong-ate, entire, enlarged at base, 

 separated by an acute sinus; nerves equal, tliick, arising from the rachis, 

 diverging towards tlio base, then approxiiuiite, parallel, forked, branches 

 uniting to form areohr that are obliquely elongate, rliomboidal in shape. 



The above is Zigno's description of Cfcnis, being an amendment of 

 that of Lindley and Ilutton. If wo alter this so as to read "leaves pin- 

 nate," and omit the items "enlarged at base, separated by an acute sinus," 

 it will apply to a very noteworthy form found in the Potomac flora. This 

 is without doubt either a true Ctcn'is, or so closely allied to it that, in the 

 absence of more definite characters, it may be placed in that genus. 



Ctenis imbricata, sp. nov. 



Plate CXXXVIII, Figs. 10-12. 



Leaf very large, [)iunate; leaflets attached bv tlio entire base, which 

 is narrowed and rounded off on both sides, to the upper fixce of the midril) 

 or stem, obtuse at their tips aiul rounded, with Ijroad, shallow, seeming 

 lobes on the under side, imbricated some distance above the base, each 

 leaflet expaiuling at that point and partly overlapping the next one; nerves 

 strong and distinct, wide apart, forking at or near the base or a short 

 distance higher up; liraiiches, so far as seen, jtarallel, anastomosing at 

 long intervals by a few iiu)sculating branches, so as to form long irregular 

 or subrhombic meshes, uppermost leaflets united; leaf terminating in a 

 leaflet in which the midnerve seems to split up into two branches ; at the 

 tips of the leaflets the anastomosis is more copious and the nerves are finer 

 and more closeh' placed. 



Locality : Fredericksburg ; very rare. 



This remarkable plant agrees (piite well with the suljgenus Ctenis, and 

 in some points it is like the figures of Cfciiis falca(((,- Lindley and Hutton, 



' Sclieuk, FosH. PUiinz. dor WtTiisdorf. Scliichten, 1.S71, PI. T. Fig. 8. 

 -Zigno, Flor. Foss. Form. Oolitir, v..l. 1, ia-)(V-'08, PI. XXIV, Figs. 1-3. 

 MON XV 12 



