YAKUT AT FOSSILS 133 



The general aspect of the tubular fossils for which the above gen- 

 eric name is proposed is greatly like that of the Ordovician Serpulites 

 dissolutus Billings. On closer comparison, however, their respective 

 compositions prove to be wholly different, the Ordovician fossils hav- 

 ing a glossy, phosphatic or chitinous shell resembling that of a Lin- 

 gula, while the Alaskan tubes under consideration are composed chiefly 

 of quartz and feldspar grains, with an occasional shred of colorless 

 mica. Thin sections show that their constituents are essentially the 

 same as those of the arenaceous shale in which they are found, the 

 main difference being that the grains are of more uniform and larger 

 average size in the tubes than in the matrix. 



In having a shell composed of cemented sand grains Terebellina 

 suggests Cuvier's Terebella, a genus of tubicolous worms living in 

 the present seas but recognized also in the Liassic and Upper Jurassic 

 of Germany. The tubes of Terebella, however, are more irregular 

 in their growth and, so far as we could learn, are always composed of 

 coarser grains ; and the latter differ further in being calcareous in- 

 stead of siliceous. Possibly the last difference has no structural sig- 

 nificance and is due solely to the mineralogical character of the sand 

 grains available to the worm in building its tubular investment. 

 Whether this is true or not, we believe the affinities of the new genus 

 are nearer Terebella than either Serpula or Serpulites. 



Terebellina palachei sp. nov. 



pi. xi, figs. 1-7. 



Tube long and narrow, subcylindrical, expanding very gradually 

 from the acuminate lower extremity ; about two-thirds of the diam- 

 eter is taken up by the central hollow. In the majority of the speci- 

 mens the greatest diameter does not exceed 2.3 mm., and some of these 

 must have had a length of over 15 cm. A number of fragments, how- 

 ever, have a diameter of from 3.5 mm. to 4.5 mm., but as the collec- 

 tion affords no satisfactory intermediate sizes we are not prepared to 

 say positively that these larger fragments belong to the same species. 

 The surface of most of the specimens presents no markings save a few 

 widely separated constrictions and annulations, and more numerous 

 transverse furrows or slits that seem to be due to weathering. On a 

 few of the better preserved fragments, however, the surface exhibits 

 more or less obscure and closely arranged transverse striae. 



As preserved, the specimens nearly always present clear evidence 

 of compression, the tube being in most cases cracked lengthwise. As 

 a rule the slabs of slightly arenaceous slate or shale on and in which 



