OLDKK I'OIOMAC OF \ IltdlMA AND MAIIVI.AM). oOl 



occurs on the saiiu' shil) and by \hv side of tlic fino spocinion of Gh/plo- 

 strohiis l>mokensis shown on PI. ('X, Fi<i. 1, collcctccl on Octol)oi- 1(5, 

 1892, at the Mount N'ci'non locaHty. The spccirnon is a fragment 45 mm. 

 long, which is depicted in PI. ('IX, i"ig. 7. Its iiiaximum width, which 

 is at one end, is 1(1 mm. This widest poi'tion seems to he tlie middle 

 part of the leaf. If narrows toward the opposite end, !)uf the true 

 termination does not seem to be preserved. When entire, the leaf was 

 prol)al)l>' narrowly elliptical in form. It looks .somewhat like a Rogersia, 

 but docs not have the nerwition of tiiat plant. So far as it rati be made 

 out, the nei'vation is jieculiai'. At the wi<l('r end, and foi- some distance 

 towaid the narrower, there is an imprint along the central line of the 

 leaf that may represent a midrib, but it is ill defined, and seems to be 

 composed of several slender nerves that were loosely vmited, and which 

 now, under the pressure to which the leaf has been .subjected, have 

 become separated in a straggling manner. Before rea(;hing the narrow 

 end of the leaf the apparent midnerve abruptly ends, seeming to .split 

 up. The other nerves, on each side of the ones just described, are faint 

 and irregular, and their course can not be certainly made out. They 

 seem to run approximately parallel with the central nerve and to 

 anastomose, forming long straggling meshes. The plant is very rare. 



ScLEROPTERis VERXoxExsi.s Ward. 

 PI. evil, Fi<j. 10. 



1895. Scleropteris vemonensis Ward: The Potomac Formation (Fifteenth Ann. Rep. 

 U. S. Geol. Siirv., lS9:5-94), p. .349, pi. ii, %s. 1, la, 2, .3. 



Professor W^ard in his paper on the Potomac formation, page 349, 

 has described this plant, and on pi. ii, figs. 1, la, 2, 3, has figured some 

 of the forms. The specimen depicted in fig. 3 is the largest one found. 

 Thirteen other scattered fragments oc(;ur in the Mount Vernon collec- 

 tions, but they are mostly small bits of ultimate pinna', showing at most 

 a few pinnules. The texture of the pinnules is thick and leathery, so as 

 to hide the nerves. In fig. 1, la, enlarged. Professor Ward has given a 

 form of this plant which differs from the normal, and which is apparently 

 its fructified form. One specimen, depicted on PI. CVTI, Fig. 10, occurs, 

 which is larger than the minute specimen given by Professor Wurd in 

 fig. 1, and which indeed is nearly as large as the magnified figure. 



