YAKUTAT FOSSILS 129 



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, 

 CylindriteSy 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- 

 Iczodictyon, and not Bythotrephis ; and the reticulated 

 species is of Cancellophycus, and not Raujfella ; 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 



