Penkollow.—Nematopkyton Orioni , n. sfi. 47 
regarding similar structural conditions to exist in the other 
species where the evidence is not so well defined. Never- 
theless, it must be remembered that the genus Nematophyton , 
as we now know it, is made up of several apparently distinct 
species of whose entire structure we know but little : and it is 
quite within the range of possibility — as is even now sug- 
gested by the striking structural differences presented by 
N. Ortoni — that when we are able to reconstruct the entire 
organism in each case, it may be found that more than one 
genus is represented, or that some of those which now appear 
distinct, may in reality be different parts of the same species. 
Our present knowledge of the genus Nematophyton shows 
that it embraces what appear to be eight distinct species as 
follows : — 
1. N. Logani, Dn. Lower Erian of Gaspe ; Silurian (Upper 
Ludlow) of England and Silurian (Cap Bon Ami) of New 
Brunswick. (Dawson) 
2. N. Hieksii (Eth.), Dn. Denbighshire grit (Silurian) of 
Wales. (Hicks) 
3. N. erassum (Dn.), Penh. Middle Erian of Gaspe (Bell) ; 
Hamilton Group (Middle Erian) of New York. (Clarke and 
Prosser) 
4. N. laxum (Dn.), Penh. Lower Erian of Gaspe. (Bell) 
5. N. tenue (Dn.), Penh. Lower Erian of Gaspe. (Bell) 
6. *N. Storriei, Barb. Silurian (Wenlock Age) of Cardiff, 
Wales. (Storrie) 
7. N. dechenianum, Solms-Laub. Upper Devonian of 
Grafrath, Germany. ( Solms-L aubach) 
8. N. Ortoni, n. sp. Upper Erian of Ohio. (Orton) 
