142 ALASKA GEOLOGY. 



in the much less regular convolution of the cord-like fossil. The 

 trend of the variation is toward Helminthopsis Heer, and Helmin- 

 thoida vaga might, with perhaps equal propriety, be referred to that 

 genus. 



Heer describes four species of Helminthoida from the Eocene of 

 Switzerland, and so far as we know the genus has not been heretofore 

 met with in older rocks. 1 One of Heer's species, H. appendiculata, 

 presents a peculiarity in the appendical prolongation of the closed 

 end of the loops, but in other respects resembles H. vaga of this 

 paper. Our H. subcrassa and H. exacta may be compared with 

 Schaf hautl's H. crassa, but both are distinguished by obvious differ- 

 ences. As to H. abnormis, it stands somewhat apart, yet may be 

 compared with certain varieties of H. labyrinthica Heer. 



Concerning the nature of these and other trail-like fossils, we are 

 wholly satisfied of their organic origin, while the fact that they often 

 lie over each other and sometimes are piled together like tangled cords, 

 proves, we believe, conclusively that they are not trails. Considering 

 their organic nature as established, some provisional position must be 

 assigned to them in nature until something definite concerning their 

 structure may be learned. In the mean time we are quite willing to 

 follow Heer and others, who view them provisionally as marine 

 plants, despite the fact that no corresponding algae are known in the 



present seas. 



Helminthoida exacta sp. nov. 



pi. xvi, fig. 5. 



The remains of this supposed marine plant resemble a convoluted 

 cord, about 1.5 mm. in thickness, folded very regularly so as to form 

 equal, narrow, slightly curved loops about 18 mm. in depth and aver- 

 aging 1.5 mm. in width. The imperfect specimens at hand indicate 

 that as growth proceeded the successive loops increased very gradually 

 in length. 



Locality. Pogibshi Island, opposite the village of Kadiak, Alaska. 



Collectors. G. K. Gilbert, B. K. Emerson, Charles Palache. 



Helminthoida subcrassa sp. nov. 



pi. xvi, fig. 3. 

 The form for which this name is proposed is represented by a 



'Since the above was written the author has discovered two large species ap- 

 parently of this genus, one in the Batesville Sandstone of the Lower Carbonif- 

 erous rocks of Arkansas, the other in the somewhat younger Strawn Formation 

 of Texas. This fact and the possible relations to Crossopodia are noted ante, 

 page 129. 



