1897.] NATURAL SCIENCES OF PHILADELPHIA. 475 



In the present condition of the literature upon tubicolous worms, 

 it is impossible for us to determine the generic position of these 

 remains, but we take them to be something of the nature of Ditrupa, 

 Hamulus or Pyrgopolon ; the massive, sculptured tube being not 

 unlike the Cretaceous groups mentioned. 



EXPLANATION OF PLATES. 



Plate X. 



(All figures natural size). 



Figs. 1, 2, 3. Dentalium dissimile var. ponderosum Gabb. 

 Fig. 4. "Dentalium rudis " Gabb. Fragments of three individ- 

 uals. 

 Fig. 5. Dentalium Tryoni.n. sp. 

 Figs. 6, 7. Dentalium Gabbi u. sp. 

 Fig. 8. " Dentalium rudis " Gabb. Fragment. 

 Fig. 9. Dentalium Tryoni n. sp. 

 Figs. 10, 12. Dentalium callioglyptum n. sp. 

 Fig. 11. Dentalium cossmannianum n. sp. 

 Fig. 13. Dentalium Gabbi n. sp. 



Plate XL 



2. Dentalium Gabbi n. sp. Enlarged view of the apex. 

 Dentalium dissimile Guppy. Enlarged view of anterior 

 portion. 



Dentalium dissimile Guppy. Enlarged view of posterior 

 end. 



Dentalium dissimile Guppy. Enlarged view of apex. 

 Dentalium pyrum n. sp. Enlarged view of aperture. 

 Dentalium pyrum n. sp. Ventral aspect, enlarged. 

 Dentalium haytense Gabb. Aperture, enlarged. 

 Dentalium haytense Gabb. Lateral aspect, enlarged. 

 Dentalium Cossmannianum n. sp. Lateral aspect of 

 anterior portion. 



Dentalium Cossmannianum n. sp. Section, enlarged. 

 Dentalium precursor n. sp. Aperture, enlarged. 

 Dentalium prozcursor n. sp. Lateral aspect, enlarged. 

 Dentalium prozcursor n. sp. Dorsal aspect, enlarged. 



