298 
PALAEONTOLOGY OF NEW YORK. 
annulations. It is more nearly related to 0. cc&lamen , but is distinguished by 
its continuous, sharp, longitudinal striae and more elevated annulations. 
This is the most abundant and extensively distributed species in the Hamil¬ 
ton group. Specimens are common in the soft shales, in the coarser beds and 
in the calcareous layers throughout the greater portion of the State. The 
specimens in the softer shales are often much broken and flattened from com¬ 
pression, but the test and surface characters are usually well preserved. From 
these have been obtained several good examples of the initial extremity of the 
shell, which is not well preserved in any other species described in this volume. 
Formation and localities. In the soft shales of the Hamilton group; on the 
shore of Seneca lake; at Ludlowville, on Cayuga lake; and in the coarser 
shales at Cazenovia, Hamilton and numerous other localities in New York. 
ORTHOCERAS CiELAMEN, n. Sp. 
PLATES XLII, FIG. 10; XLITI, FIG. 15; LXXXII, FIG. 16; CXIII FIGS. 22, 23. 
Orthoceras nuntium and Orthoceras crotalum, Hall (in part). Illustrations of Devonian Fossils: Cephal¬ 
opoda. Explanation of plates 42, 43. 187(5. 
Shell straight, regularly and gradually enlarging to the aperture. Transverse 
section circular. Apical angle about 5°. Initial extremity unknown. 
The extent of the chamber of habitation has not been observed. Air- 
chambers regular, having a depth of two mm. where the tube has a diameter 
of nine mm. 
Septa with a concavity equal to the depth of the air-chambers; ornamented 
with a small, slightly-elevated areola, and fine, radiating, vascular markings, 
which extend from the insertion of the siphuncle to the margins. Sutures 
straight and horizontal, more frequent than the annulations of the tube. 
Siphuncle large, slightly excentric, having a diameter of 1.75 mm., where 
the tube has a diameter of nine mm. Its elements in the interseptal spaces 
have not been observed. 
Test thin, having a thickness of about .25 mm. Tube ornamented with 
regular, sharp annulations, which increase in frequency from the chamber of 
habitation to the apex. Where the tube has a diameter of sixteen mm. the 
