CEPHALOPODA. 37 



siphuncular significance. In other characters it resembles sonic described 

 species of gastropoda belonging to the genus Porcelli a ; bul with the present 

 material it is difficult to make a satisfactory determination. 



The specimen illustrated shows three volutions and measures 1(H) mm. in 

 greatest diameter. 



Distribution. In the sandstones of the Waverly group, Warren county, Pa. 



TrOCHOCERAS ? (Go.MOCERAS I) PANDUM. 



PLATE CX\ II. FIGS. 3-5. 



Trockoeeras .* (ffonioeera. pandum, Hall. Pal N. V.. vol. v. pt. 2, p. 4iU. pi. iii. fig. -t. 1879 



No additional specimens of this species have been obtained since the original 

 publication in 1879, and its generic relations are still uncertain. In addition 

 to its comparison with some associated forms of Trochoceras from the Schoharie 

 grit, as noticed in Pal. N. Y., vol. v, pt. 2, p. 403, it may also be compared 

 with Gomphoceras fax. illustrated on plate exxii. 



NAUTILUS, Breynius. 1732. 



Nautilus oriens. 



PLATE CXXVI, FIG. 2. 



Nautilus oriens, Hall. Pal. N. Y., vol. v. pt. 2, y. 4'jn. 1879. 



Nautilus Hyatti. 



PLATE CXXVI, FIG. 1. 

 Nautilus Hyatti, Hall. Fifth Ann. Rept. State Geologist. Expl. pi. (126) 11, fig. 1. 1886. 



In its general characters, this species is closely related to N. burinum (Pal. X. 

 Y.. vol. v, pt. 2, p. 412). The shell is more rapidly expanded than in that 

 species, especially toward the apex. The volutions are free. The transverse 

 section is sub-circular in the apical portion of the shell, broadly oval through the 

 chamber of habitation, and with no dorsal sinus produced by the contiguity of 

 the volutions as in N. bucinum. 



The specimen is an external mould preserved in an argillaceous concretion, 

 and the form and surface characters of the shell are well preserved. The sur- 



