Maryland Geological Survey 299 



siderable size, one being 39 cm. in length by 17 cm. in diameter. Tliey 

 are not uncommon and are considered by many as petrified palms, while 

 others look upon them as fragments of bones of huge dinosaurs. 



Occurrence. — Patapsco Formation. Valleys of Stony Eun and Deep 

 Eun near Severn, Anne Arundel County, Patuxent Neck, Prince George's 

 County, Maryland. 



Collections. — Johns Hopkins University, Goucher College. 



INCERTAE SEDIS 



Genus SCLEROPTERIS Saporta 



[Pal. Franc, tome i, 1873, p. 364] 



This genus was established by Saporta for the reception of certain 

 forms of supposed ferns of Jurassic age previously referred to Loxop- 

 feris Pomel, Sphenopteris Brongn., Dichopteris Zigno, and Pachypteris 

 Brongn., but without completely absorbing any of these genera. He 

 characterized it as follows : " Frons rigide coriacea bi-tripinnata, pinnis 

 pinnatipartitis, pinnulis basi plus minusve constrictis in rachin angus- 

 tissime alatam latere inferiori decurrentibus integris vel antice incisis 

 lobulatisque ; nervatio immersa, ssepius imperspicua, ut manifesta fit, 

 e nervulis paucioribus a basi ramosis latere dorsali pinnularum oblique 

 prodeuntibus constans." 



It seems probable that ScleropteriSj, as at present constituted, is a 

 composite genus, certain species of which may be ferns while others, 

 such as those formerly referred to Pachypteris Brongn., may well be 

 cycadaceous.* 



As developed in the Potomac beds it is represented by bi- or tripinnate 

 coriaceous fronds with pinnatifid pinnae more or less constricted and 

 decurrent at the base, entire or incised on the anterior margin, with a 

 flabellate venation immersed in the leaf substance. The genus is well 

 developed in. the middle and the Upper Jurassic, both in this country 

 and Eurasia, and has several Lower Cretaceous representatives. These 

 include, in addition to the following Potomac form, two species from 

 the Lakota formation of eastern Wyoming, and a third from the ISTeo- 



^ See Krasser, Jahrb. k. k. geol. Reichs., Bd. xlv, 1895, pp. 39-49. 



