CEPHALOPODA. 
29 
Orthoceras expositum. 
PLATE CXVIII, FIG. 2. 
Orthoceras expositum. Hall. Fifth Ann. Rept. State Geologist. Expl. pi. (118) 2, fig. 2. 1886. 
Shell large, straight, gradually enlarging to the aperture; transverse section 
sub-circular. Apical angle five degrees. Initial extremity unknown. 
Chamber of habitation long, regularly expanding to the aperture, length 
more than twice the diameter of the tube at the last septum. Air-chambers 
7 mm, in depth where the tube has a diameter of 37 mm., becoming regu¬ 
larly shallower toward the apex of the tube. 
Septa thin, concavity deeper than the depth of the air-chambers. The 
apical portion of the shell is partially filled with an irregularly vesiculose 
organic deposit, 
Siphuncle moniliform, excentric. 
Test not preserved. The impression of the shell in the rock shows that 
the surface was marked by lamellose concentric lines of growth. 
The specimen illustrated has a length of about 300 mm,, of which 125 
mm. belong to the chamber of habitation. 
Numerous fragments of this species are preserved in an iron-ore bed, from 
Bradford county. Pa. The specimens consist of internal moulds in a ferruginous 
sandstone, or of calcareous shells imbedded in the sandstone. 
Distribution. In an iron-ore bed of the Chemung group. Canton, Bradford 
county. Pa. 
Orthoceras consortale. 
PLATE CXVIII, FIGS. 3-5. 
Orthoceras consortale. Hall. Fifth Ann. Rept. State Geologist. Expl. jil. (118) 2, figs. 3-5. 1886. 
Shell straight, rapidly expanding from the apex to near the aperture; trans¬ 
verse section broadly oval. Apical angle ten degrees. Initial extremity 
unknown. 
Chamber of habitation not fully shown in the specimens observed, appar¬ 
ently short and constricted near the aperture. Air-chambers 5 mm. in 
