306 Systematic Paleontology 



they were once attached to a common rachis, not now preserved. The 

 pinnae or lobed pinnules partly overlap. The parts that are preserved 

 appear to be the terminal ones of the pinna or pinnules, and they are not 

 sufficiently well preserved to give their dimensions and shape. The 

 nature of the incisions of the lamina, which represent either lobes or 

 pinnules, can be made out and the nervation is remarkably distinct. 

 This specimen is without number or locality label, but the Arlington 

 material is so distinctive that there can be no doubt that it is from that 

 locality. 



" The lobes or pinnules are very obliquely incised and are oblong in 

 form, with the free ends obtuse lancet shaped. The incisions visible 

 are not cut down to the midrib, but indicate that lower down on the 

 portions shown they may be so, constituting pinnules. The midnerve or 

 rachis of the pinna is distinct and somewhat flexuous. On each side of 

 this midnerve parent nerves depart at a very small angle to enter the 

 pinnae or lobes. The parent nerve forks at long intervals, the principal 

 branch of each fork keeping near the middle of the pinna or lobe, while 

 the other branch forks some distance up. These minor nerves are quite 

 remote from one another and sharply defined, though not very strong. 



" While this fern cannot be fully made out, it is clearly different from 

 any previously found in the Potomac beds. It is confined to the Arling- 

 ton localities." — Fontaine, 1906. 



Any further discussion of such incomplete remains can serve no useful 

 purpose. 



Occurrence. — Arundel Formation. Arlington, Maryland. 



Collection. — Goucher College. 



Order LYCOPODIALES 



Family SELAGINELLACEAE 



Genus SELAGINELLA Beauvois 

 [Prodr. Aetheog., 1805, p. 101] 



The Paleozoic representatives of the order Lycopodiales (Lepidoden- 

 dron, Sigillaria, etc.), as is well known, were dominant members of that 



