;.;s PALAEONTOLOGY OF NEW YORK. 



GOMPHOCERAS SOLIDUM, n. Sp. 

 PLATE XCIII, FIG. 9. 



Shkll large, straight, biconical. Transverse section circular; longitudinal sec- 

 tion sub-rhomboidal. The plane of greatest transverse section is through the 

 chamber of habitation, distant from the last septum about one-fourth the 

 length of the chamber. Tube expanding regularly to the point of greatest 

 gibbosity, and rapidly and abruptly contracting to the aperture. Apical 

 angle about 35°. 



Chamber of habitation large; length somewhat less than the diameter of 

 the tube at the last septum. The sides slope regularly and rapidly to the 

 aperture. Crenulated band broad, marked by indistinct lurrows and striae, 

 which are carried over the cast of the chamber walls. 



Aperture large ; not satisfactorily observed. 



Air-chambers regular, having a depth of six mm., and showing no appre- 

 ciable variation in the length of sixty mm. Septa and siphuncle not 

 observed. Sutures straight and horizontal. 



Test and surface-markings unknown. 



The internal mould shows the general form of the shell, with the regular 

 and frequent air-chambers. 



The specimen figured, preserving the chamber of habitation and eleven 

 air-chambers, has a length of 148 mm., and a diameter at the point of 

 greatest gibbosity of ninety mm. 



This species resembles G. Fischeri, with which it is associated, but is distin- 

 guished by its general form, the rapid contraction of the chamber of habitation, 

 the point of greatest gibbosity, the character of the crenulations, and the depth 

 of the air-chambers. In G. abrupium the apical angle is apparently much 

 greater, and the comparative volumes of the septate portion and the chamber 

 of habitation very different. 



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

 Manlius, N. Y. 



