(356 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



Onoclea MINIMA II. sp 

 PI. LXXVII, figs. 11-15. 



Fertile frond unknown; sterile frond small, apparently deltoid in 

 outline, deeply pinnatifid into short, rounded, obtuse pinnae, which are 

 perfectly entire or are cut into few large, coarse teeth; nervation as in the 

 living 0. sensibilis. 



This fine little species is represented by a dozen or more specimens, 

 the best of which are figured. They are all apparently fragments, and 

 consequently it is impossible to make out the real shape of the frond with 

 any certainty. One of the most perfect specimens (fig. 13) is about 3.5 

 cm. long, and represents the upper portion of a frond or possibly pinnule, 

 if it is a large compound frond. The larger fragment (fig. 15) is 4.5 cm. 

 long' and about 4 cm. broad, but it is broken at both ends and there is no 

 means of determining how long- it was originally. Fig. 12 at first sight 

 seems to be entirely different from the others, but on comparing it with fig. 

 14 the only difference observable is that one is cut into a few coarse teeth 

 and the other is entire. The nervation seems to be the same in all and to 

 be identical with that of the living sensitive fern. 



Regarding this interesting species, I am somewhat uncertain as to the 

 shape of the frond, and less so as to the genus to which it belongs. Two of 

 the most perfect forms (figs. 11, 13) seem to have come from the upper 

 portion of a frond similar in general shape to the sterile frond of Onoclea 

 sensibilis; but, on the other hand, figs. 12 and 14 have much the appear- 

 ance of being deeply lobed pinna?, resembling some of the lower ones in 

 0. sensibilis. More material will be necessary to settle this point, but in 

 the meantime the species is characteristic enough to be readily distinguish- 

 able, and hence is available for geological purposes. 



This species was at first thought to be identical with a plant that has 

 been described under the MS. name of Woodwardia crenata, which comes 

 from Point of Rocks, Wyoming. This latter is known only from a mere 

 fragment, however, and if additional material could be obtained it might 

 show them to be the same. . At present W. crenata may be distinguished as 

 being- much larger and in having undulate-crenate margins wdiich are 

 minutely serrate. The nervation is practically the same in both. 



Onoclea minima has some resemblance to 0. sensibilis fossil is from the 

 Fort Union group, near the mouth of the Yellowstone. It differs in being 



