Maryland Geological Survky 691 



chambers can be noticed in the tube for a length of 125 nun. Septa thin, 

 deeply concave. Sutures somewhat curved, not deeply impressed on tlie 

 internal mould. Siphuncle moniliforni, excentric, distant more than one- 

 third the diameter of the tube from the ventral side. Test marked by 

 irregular lamellose lines of growth, which make a distinct retral curve 

 on the ventral side of the tube. Internal mould smooth." Hall, 1888. 



The fragments observed are indistinguishable from Hall's type. 



Occurrence. — Jennings Formation, Ciieimung Member. Williams 

 Eoad, on Polish Mountain, 2043 common. 



Collection. — Maryland Geological Survey. 



Orthoceras cf. demum Hall 

 Plate LXXI, Figs. 14, 15 



Orthoceras demus Hall, 1879, Pal. of N. Y., vol. v, pt. ii, p. 311, pi. xc, flgs. 

 1, 4, 5. 



Description. — ■" Shell straight, regularly enlarging. Transverse sec- 

 tion circular. Apical angle 6°. Initial extremity unknown. Chamber of 

 habitation not observed. Air chambers regular, increasing in frequency 

 toward the apex, having a depth of from two to three mm. ; varying to this 

 degi-ee in the length of forty-five mm. Septa smooth, thin, having a con- 

 cavity greater than the depth of the air chambers. Sutures straight and 

 horizontal. Siphuncle small, excentric, and at the septa is distant from 

 the nearest point on the margin about one-third the diameter of the tube. 

 The other elements have not been observed. Test not preserved, surface 

 markings unknown. The internal mould is essentially smooth." Hall, 

 1879. 



Occurrence. — Jennings Formation, Chemung Member. Town 

 Creek, 37G0; Hancock, 2223. 



Collection. — Maryland Geological Survey. 



Orthoceras filosum Clarke 



Plate LXXI, Figs. 12, 13 



Orthoceras filosum Clarke, 1885, Bull. 16, U. S. Geol. Survey, p. 52, pi. ii, 

 figs. 12-14. 



