CEPHALOPODA.  281 



can only be verified by a critical examination of numerous individuals in all 

 conditions of preservation, and from sections made with a view of ascertaining 

 the extent and position of the organic deposit. 



This species, so far as known, is confined within the limits of the Goniatite 

 limestone in the Marcellus shales, and is the " Marcellus orthocera" of Vanuxem 

 (Report of the Third District, p. 149: 1842), and mentioned on p. 147 of his 

 report as " a large Orthocera, the Marcellus." Dr. Saemann cites Cazenovia, 

 Madison county, N. Y, as the original locality for his species. This is 

 an evident error in the locality reference ; but there is no doubt as to the 

 present identification, as he describes this species, the formation, and its 

 association with Goniatites, Gomphoceras, etc. 



Formation and localities. In the Goniatite limestone of the Marcellus shale, 

 at Manlius, Marcellus, and other localities in the central portion of the State. 



Orthoceras fdstis, n. sp. 



FLATXS I WXIII, KIG. 11; CXIII, KIGS. 16, 17. . 



Shell straight, very regularly and gradually enlarging to near the aperture. 

 Transverse section circular. Apical angle 4J°. Initial point unknown. 



Chamber of habitation short, having a length of about twice the diameter 

 at the last septum, with several obscure undulations throughout the length, 

 except the one near the aperture, which is a very distinct and abrupt 

 constriction following the sinuosities of the margin. Aperture abruptly con- 

 tracted, with two or three broad sinuosities in the margin. Air-chambers 

 regular, numerous, having a depth of five mm. near the grand chamber, 

 where the diameter of the tube is thirty-five mm. 



Septa thin, smooth near the outer chamber, having a concavity equal to 

 an arc of nearly 90°. Sutures straight and horizontal. 



Siphuncle central, straight, nearly cylindrical, abruptly constricted in its 

 passage through the septa, where it has a diameter equal to about two-thirds 

 as great as in the air-chambers. Its diameter is 3.5 mm. where the tube 

 has a diameter of about thirty-five mm. 

 36 



