522 MESOZOIC FLORAS OF UNITED STATES. 



the side that is preserved there is attached a part of the himina of the 

 leaf that indicates a width for the himina on that side of at least 5 cm. 

 This portion of the lamina is distorted in the upper portions, it being 

 bent fonvard. The width may have l)een greater than 5 cm. This 

 indicates for the entire leaf a width of at least more than 10 cm. The 

 portion of the lamina preserved is not segmented. The nerves are 

 parallel, closely placed, and single. They go off from the midrib at a 

 large angle and are slightly curved fonvard. 



The plant agrees closely with Plat y pterygium densinervc Font., a 

 plant highly characteristic of the Fredericksburg locality in the Rap- 

 pahannock group of the Lower Potomac. This is described in Mono- 

 graph X^^ pp. 169-170. The Fredericksburg plant is very irregularly 

 segmented and the wider segments in it are broader than the portion 

 shown in the Langdon specimen. The latter may be compared with 

 fig. 1 of pi. xxii of the work quoted. The small amount of material 

 does not permit a positive identification with P. densinerveJ^ 



" One of the specimens that I collected in May, 1897, originally showed a narrow strip, about 2 cm. wide 

 at one end and only 3 mm. wide at the other, with a length of 5 cm., across which fine nerves could be seen to 

 run. indicating a cycadaceous leaf. This was returned by Professor Fontaine with the following words on the 

 label: "Fragment of a large cycad leaf not determinable." In the manuscript of his report this specimen 

 was described as follows: 



"Undetermined large cycad. A. fragment of the leaflet of a cycadaceous plant was found which indicates 

 a leaf of considerable size, larger than that of a Zamitcs, from which it differs in other respects than size. Not 

 enou" h of the plant was obtained to show anything defmite, as the specimen is a small fragment of a leaflet." 



On a casual examination of the specimen I perceived that the fine nerves ran under the adjacent rock 

 substance, and a few taps with a hammer caused the rock to cleave on the plane of the leaf and brought out 

 the amount of surface that is seen in the figure with 4 cm. of attachment to the midnerve, which is on the side 

 opposite to that originally exposed and was not visible in the specimen as first examined by Professor Fontaine. 



I therefore returned it to him on March 12, 1903, and in the letter accompanying it I said: 



"I am sending you in a small box by mail a specimen from the Langdon locality, on which you recognized 

 a small portion of a large cycad leaf, and so labeled it. I have worked out all that existed in the specimen 

 and it is quite distinctive. It seems to be entirely difl'erent from anything else in the Potomac formation. 

 You can see the large midrib to which a wide blade is attached on one side, and you can follow the fine nerves, 

 passing entirely across the specimen, with a somewhat upward curve. So far as I can see, there is no areola- 

 tion or anastomosis. It seems somewhat like a Nilsonia of the nonsegmented group." 



He returned the specimen the next day with the description and identification given above. 



There should properly be no genus Platypterygium. Schimper, in Zittel's Handbuch, p. 22,5, which was 

 in the second fascicle, dated 18.S0, in treating the genus .\nomozamites, created a subgenus Platypterygium 

 for certain verv large-leaved forms, the chief of which are the Pterophylluiii Biaiinsii Sclienk, P. printeps 

 Oldh. ic Morr., P. MrdlicoUiannrn Oldh. & Morr., and P. Morrisiannm Oldh., all of which he had already 

 referred to .\nomozaniites in his Traitt' de Paleontologie Vcgctale, Vol. II, pp. 142-143, 1870, mthout placing, 

 them in any subgenus, Feistmantel, in his Fossil Flora of some of the Coal Fields of Western Bengal (Foss. 

 Fl. Gond. Syst., Vol. IV, Pt. II), p. 37, accepted Schimper's subgenus Platypterygium, calling it such, and 

 referring to it his Anomozaniite$ (Plerophyllum) Balli, but treating it as Platypterygium BaUi, thereby virtually 

 raising Platypterygium to generic rank. Professor Fontaine, in his Potomac Flora (see synonymy above). 



