JIHASSIC KI^OHA OF DOlCiLAS COl'NTY. OHEG. 55 



•abundant. The specimens are generally very fragnieiitaiy, aiul, what is 

 noteworthy, the parts preserved are often in a good state of preservation 

 in that the epidermal tissue is intact, and the {)laiit substance gives a 

 black carbonaceous film on the rock. The parts do not seem to have 

 suffered much from maceration due to long floating in water, hence the 

 fragmentary state nnist be produced by some other cau.se. The coniferous 

 fo.ssils also show a great conmiiiuition of parts, with a good preservation 

 of tlie })laiit sul)stance. The cycads do not sliow so extensive a laceration, 

 although they, too, ;iie niucli broken, while the parts that are shown are 

 wonderfully well preserved. 



Family CYATHP]ACK.E." 



Genus DICKSONIA l>Il.-iiti('r. 



I)u KsoNiA oREGONENSis Foiitaiiie n. sp. 



PI. VI, Fijis. 3-9; PI. VII. 



1898. l>ni<i]t1er'iK iiKHidciirpa (Font.) Kn.: Bull. U. S. Geol. Surv., No. 152, p. 92. 

 1111)1). llnjDjittrtx iiKiiiDCdrjxi (Font.) Kn. Waril: Twentieth Ann. Rej). I'. S. Geol. 

 Surv., 1898-99, Pt. II, p. 369. 



This plant was probal)ly arl)orescent. Both fertile and sterile forms 

 were obtained. Most of the specimens show^ fertile forms. The largest 

 specimens seen with attached pinnse give no more than a tripinnate 

 division but the.se were evidently fragments of much larger compound 

 pinnse. Fragments of a rachis not showing attached pinnae, but so asso- 

 ciated wdth this fern as to indicate clearly that they belong to it, were 

 obtained that are 8 mm. wide. The ultimate pinna» are very short, not 

 stu'passing 45 mm. in length. The pinnules with entire margins, such as 

 are found in the upper portion of the compoimd pinna» and in terminal 

 parts of the subordinate pinna^, are quite small, being not more than 3-4 

 mm. long and 2-3 mm. wide. They are narrowed toward the base and 

 elliptical in form. They are attached by this narrowed base so as to make 

 a small angle with the rachis, and are decurrent, forming a very narrow 

 wing. The basal pinnule on the upper side of the ultimate pinna is larger 

 than the rest and is more incised, having imdulate or dentate margins 



"Wlien niyfir.sl paper \va.s written the part of Englcr and Prantl's system containing tlic l'tcri(i(i|)liyta 

 was a.s yet unpiil)lisli<'(i. It lias sinee been completed, and their subdivisions into families will he followed 

 in the present paper. — L. I". W . 



