PALEONTOLOGY OF NEW YORK. 



aniiulations. It is more nearly related to 0. calamen, but is distinguished by 

 its continuous, sharp, longitudinal striue and more elevated aniiulations. 



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 CjElamen, n. sp. 



PLATES XLII, FIG. 10; XLM, FIG. 15; I.XXXII, 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. 1876. 



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 aniiulations 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 



