S16  PALEONTOLOGY OF NEW YORK. 



in the form and characters of the siphuncle, as well as in the other elements of 

 the shell, as to render the removal of the genus Bactrites to the Goniatitidoe 

 undesirable. It seems to possess transitional features between the families of 

 Goniatitidte and Orthoceratidoe ; and I prefer to arrange it, for the present at 

 least, with the latter. 



Bactrites clavus, n. sp. 



ri.ATKS LXXXIV, FIG. 15; CXIII, FIGS. 1-5. 



Shell slender, straight, regularly and gradually enlarging to the aperture. 

 Transverse section elliptical. Dorso- ventral diameter the longer, having a 

 ratio of 2 to 3 with the lateral diameter. Tube subcarinate on the dorsal (?) 

 side. Apical angle a little more than 1°. Initial extremity unknown. 



Chamber of habitation well developed, having a length of more than six 

 times the dorso-ventral diameter at the last septum, regularly enlarging to 

 the aperture. Air-chambers regular, with a depth of three mm., or equal 

 to the lateral diameter of the tube, from which they do not vary perceptibly 

 in the length of sixty mm. 



Septa thin, smooth, moderately concave along the lateral diameter, and 

 with a concavity equal to an arc of 140° in a dorso-ventral direction. The 

 sutures form a broad retral curve over the lateral faces of the tube, extend- 

 ing forward over both the ventral and dorsal sides. Immediately over the 

 insertion of the siphuncle they curve more or less abruptly backward, form- 

 ing the "dorsal lobe," which corresponds to a similar feature in Goniatites, 

 and probably marks the ventral side of the shell. The sutures meet in an 

 obtuse angle at the carina along the dorsal (?) side. 



Siphuncle small, submarginal, indenting the septa, having a diameter of 

 one-half of one mm. Its elements in the interseptal spaces are unknown. 



Test and surface ornaments not preserved on any of the specimens. 



Internal mould smooth, with the sutures but slightly impressed. 



An individual, preserving a portion of the chamber of habitation and 

 twenty-three air-chambers, has a length of ninety-five mm.; with dorso-ven- 



