CEPHALOPODA. 
275 
and a diameter at the aperture of ninety-five mm. A septate fragment 
containing thirteen air-chambers has a length of 155 mm. 
This species differs from 0. Bebryx in its larger size, more distant septa, and 
cylindrical siphuncle. It more nearly resembles 0. Pelops and 0. Zeus of the 
Schoharie grit, but it has not the constriction of the chamber of habitation of 
the latter, and the prominent areola around the siphuncle of the former species. 
Formation and localities. In the Hamilton group on Lake Erie shore, and at 
Otisco, Onondaga county, N. Y. 
Orthoceras Bebryx. 
PLATES XXXVm, FIG. 10 ; XXXIX, FIG. 2; LXXXITI, FIG. 14; LXXXIV, FIGS. 11, 12. 
Orthoceras Bebryx, Hall. Illustrations of Devonian Fossils; Cephalopoda. Explanation of plate 39, 
figs. 1, 2. 18715. 
Shell robust, straight, regularly enlarging from the apex. Transverse section, 
allowing for the degree of compression, subcircular. Apical angle eight to 
ten degrees; the variation being due to the compressed condition of the 
specimens. 
Chamber of habitation not fully observed. Air-chambers regular, increas¬ 
ing in depth from the apex, and varying in different individuals from six to 
ten mm. 
Septa smooth and thin, so far as observed. Sutures, in specimens not 
distorted by compression, straight and horizontal. 
Siphuncle moniliform, expanding between the septa, and having a diameter 
equal to, or two-thirds, the depth of the air-ehambers. The septa are usually 
macerated, or broken from compression, and the position of the siphuncle 
has not been satisfactorily determined. One small fragment, referred to 
this species'with doubt, retains the septa, and shows the siphon in a slightly 
excentric position. 
The test has not been preserved. The casts of the interior indicate a 
transversly lamellose-striate surface. 
A fragment, embracing a portion of the chamber of habitation and seven¬ 
teen of the adjacent air-chambers, has a length of 220 mm. 
