DESCKIPTION OF THE SPECIES. 65 



Equisetum Lyklli Mantell. 



Plate I, Fig. 7; Plato II, Figs. 4, 5. 



Schenk* says of E. L>/elU, from the Wealden of England: "It lias a 

 brancliiug stem, with iutenioiles 2 ^ long, and is lO"" to 13"'" in diameter. 

 The branches are 5'"" in diameter. The sheaths are 1"° long, and the teeth 

 are linear and acnminate." 



The Potomac plant in most of these features agrees closely with E. 

 Li/elli Tiie form given in Pi. II, Fig. 4, and the smaller stem in Fig. o of 

 the same plate, are jirobably branches. The resemblance is especially 

 close in the long, narrow, and remotely placed teeth. This plant has also 

 a marked likeness to E. LmitanicAim Ileer, from the Jurassic of Portugal.^ 



Localities: The form given in PI. I, Fig. 7, comes from Fredericks- 

 burg, and the others from the fishing hut above Dutch Gap Canal. 



Rhizome op Equisetum, sp.? 



Plate II, Fig. 8. 



Plate 11, Fig. 8, depicts a fossil which appears to be the rhizome of an 

 eipiisetum. It shows no sheaths, is jointed at unequal intervals, and has 

 on the upper surface three or four narrow prominent ridges. It seems to 

 be decorticated, and is probably the rliizome of E. LijcUi. 



Locality: Fredericksburg; only one specimen was found. 



Equisetum Marylandicum, sp. nov. 



Plate II, Fig. 10. 



Stems branching copiously; branches long and slender; surfiice 



smooth; branches 1.5 and less in diameter; interiiodes 15'"'" or a little 



more in length; slieaths slightly swollen, 2""" long; teeth visible on the 

 branches, three to four in number, very short, oval in shape, and termina- 

 ting in short acute tips. 



Localities: Not rare on Belt and Covington streets, Baltimore. 



Specimens of this little Equisetum may be found occasionally in the 

 shale, especially of Covington street. They are mostly in the form of 



' Die foss. Flor. d. nordwestdeutsch. Wealdeuforniatiou, Cassel, 1871, p. 5. 

 -Compare Heer'a Coutrib. Fl. Fos8. Portugal, Lisbonue, 1881, PI. VIII, Fig8. 1-6. 

 3ION XV 5 



