DESCRIPTION OF THE SPECIES. 125 



with n winged racliis : lower pimiules witli oblong- lobes rounded at the 

 ends, cut very obliquely and more or less deei)ly, passing- towards the 

 tips of the ultimate pinnaj into oblong-obtuse lobes all minutely tootlit'<l 

 on the summits ov terminal margins; nerves distinct, divurging flabellately 

 in each lobe and forking several times; the uiidnerve of the pinnules 

 splitting up towards its sunnuit 



Locality : ITill-side near Potomac Run ; rare. 



This {dant in the position of the. toothing resembles Sphenopter'is 

 (icrodvidata, but the lobes are narrower and the rachises winged, characters 

 not found in that species. 



Thyksoptekis divaricata, sp. nov. 



Plate XXXVII, Figs. 5-S ; Plato CLXX. Fig. 1. 



Frond tripinnate ; principal rachis slender, .slightlv flexuous ; ultimate 

 |)inua' remote, alternate, short; jienultimato piniuv terminating usually in 

 a three-lobed segment ; pinnules of the lower part of the frond and com- 

 pound pinuic cut more or less deeply and quite ob]i(piely into oblong or 

 ovate lobes, the two basal lobes being cut down nearly to the midncrve, 

 often with three teeth, diverging more or less widelv. Towards the tip of 

 the ultimate pini^-c and the summit of the frond the ])innules pass througli 

 toothed elliptical ))iiiiuiles into simple pimiules and lobes; midnerve of the 

 pinnules splits up at the tij) into l)i-anclies ; nerves go otf obli(piely into 

 each lobe or tooth, composed in the lower ones of a midnerve, which sends 

 off alternately on each side branches forked or simple, conqjosed in the 

 upper ones of forking and simple nerves. 



Localities: Fishing hut above Dutch Gap Canal; Fredericksburg; 

 red clav ball in banks of Dutch Gap Canal ; rather rare. 



'l^his plant is noteworthy for the peculiar divergence of the two lowest 

 lobes in the pinnules and the extreme slenderness of the primary rachi.s. It 

 is not common, and appears not to be nearly allied to any described fossil. 



Thvrsoptkris Meekiana, sp. nov. 



Plate XXXVIII, Figs. '^-4, S: Plato L, Figs. 7, 8; Plate LI, Fig. 3. 



Frond tripinnate, arborescent; pinnse and pinnules much crowded; 

 I'achises, especially the principal ones, as a rule, very stout; ultimate 



