346 PAL.KOSTOLOGY OF NEW YORK. 



a truncation of the apex among the species here described. The absorption or 

 ( icatrizing of tbe apical portion of the tube evidently occurred after the indi- 

 viduals had reached a mature development. The small examples all show the 

 attenuate apex, which, in the larger specimens, is rounded, and preserves a 

 distinctive difl'erence in the external markings of the test. The specimen pre- 

 viously indicated as C. gibbosum is a small, gibbous individual, with the exterior 

 layer of the test partially exfoliated, and should evidently be included in the 

 present species. Other specimens have been observed, which present the tran- 

 Mtions in form to the large subcylindrical specimen represented in fig. 2, pi. 45. 

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

 Schoharie, and near Manlius, N. Y. 



GOMPHOCERAS PINGUE, n. 8p. 

 PLATES XCIV, FIG. 9 ; XCV, FIG. 6. 



Shell small, gibbous, slightly arcuate. Transverse section very broadly oval 

 or subcircular. Point of greatest gibbosity posterior to the middle of the 

 chamber of habitation. Apical angle about 30°. 



Chamber of habitation gibbous, with the sides convex, and sloping gradu- 

 ally to the aperture. Crenulated band not well defined, but the markings 

 are preserved over the cast of the walls of the air-chambers as broad, shallow, 

 longitudinal furrows. 



Aperture unknown. 



Air-chambers regular, having a depth of about four mm. Septa smooth, 

 moderately concave. Sutures, in uncompressed specimens, straight and hori- 

 zontal. Siphuncle not observed. 



Test and surface-markings unknown. Internal mould smooth, with the 

 exception of the crenulations over the walls of the air-chambers. Sutures 

 but slightly impressed. 



A fragment embracing a portion of the chamber of habitation, with five 

 attached air-chambers, has a length of fifty mm., of which about thirty mm. 

 pertain to the grand chamber, which has a greatest transverse diameter of 

 forty mm. 



