YAKUTAT FOSSILS 131 



our species is not strictly the same as its European repre- 

 sentative, P. magnum. Then Heer describes one insuf- 

 ficiently illustrated species from undoubted Liassic rocks, 

 which is very close to P. singulare, and to which we 

 might have referred the smaller of the two Kadiak species 

 had the illustrations of the older species been as copious 

 as those of the younger one. Finally, the specific char- 

 acters of Palceodictyon are so vague and variable, and 

 with the general simplicity of the fossilized plant so few, 

 that specific identifications necessarily are more or less 

 doubtful. Indeed, we have seen black inosculating films 

 in the Waverly shales of Kentucky and certain Carboni- 

 ferous shales in Texas that we are really at a loss to dis- 

 tinguish from the Eocene species figured by Heer or from 

 the Kadiak species. 



The direct evidence for the upper Liassic age of the 

 slates under consideration is the presence in them of four 

 European species characterizing that age, namely, Chon- 

 drites divaricatus F.-O., C. alpestris Heer, Helmin- 

 thopsis magna H. and H. ? labyrinthica H. The latter 

 genus so far is reported only from the Lias, but Chon- 

 drites ranges from the Lias, and possibly from the Trias, 

 on to the Tertiary, so that the genus can be used only in 

 determining the lower limit. The species, however, seem 

 to be sufficiently characteristic and defined to justify con- 

 siderable reliance on their evidence. 



Besides the fucoids the only fossils afforded by the 

 Kadiak localities are (i) numerous shells of a tubicolar 

 worm and (2) several casts of a pelecypod shell. The 

 evidence of these fossils is purely inferential, but so far as 

 it goes it corroborates that of the upper Liassic species 

 mentioned in the foregoing paragraph. The worm tubes, 

 to which we have applied the name Terebellina palachei, 

 compare in form with the Ordovician genus Serpulites, 

 but in being composed of cemented grains of sand they 



