YAKUTAT FOSSILS 
I29 
commonest, are often very similar. Thus the Ordovician 
Arthraria , Bythotrephis , Paleophycus, Rauffella , and 
certain undescribed forms, have, respectively, their corre- 
ponding types in Fucoides moeschi Heer, Chondrites , 
Cylindrites , Cancellophycus , and Palceodictyon of the 
Lias. One might say that this similarity in expression 
argues for an inorganic origin of these reappearing types. 
But this assertion would not be warranted, since, aside 
from the types peculiar to each fucoid horizon, the reap¬ 
pearing types are represented in each horizon by sets of 
species distinguishable by minor peculiarities from those 
of the corresponding type in another horizon ; and if we 
could compare in these extinct marine floras the fructifica¬ 
tion and other features that are considered important in 
classifying recent algae, the apparently close resemblances 
between the successive floras would probably resolve 
themselves into mere family likenesses. 
Coming to a more detailed comparison of the Yakutat 
fucoids with those characterizing the various horizons 
mentioned, we find that they indicate some post-Paleozoic 
time, for the branching forms are of Chondrites and Pa¬ 
lceodictyon, and not Bythotrephis ; and the reticulated 
species is of Cancellophycus , and not Rauffella ; while 
the new generic types are so far quite unknown in any of 
the Paleozoic fucoid horizons. Forms of the true Hel - 
minthopsis type also are so far unknown in Paleozoic 
rocks, but Helminthoida , though apparently restricted to 
the Eocene in Europe, has recently been discovered in 
two Lower Carboniferous horizons in Arkansas and 
Texas, and possibly is represented among the Silurian 
forms referred to Crossopodia McCoy e. g., C. scotica 
Nicholson (?McCoy). 
Now, according to the evidence of its fucoids, and as¬ 
suming, of course, that we are not dealing with a new 
horizon, the slate of Kadiak must be referred to either the 
