104 [Senate 



CYRTOCERAS TRANSVERSUM ( n. s. ). 



Shell moderately curving, somewhat flattened upon the ventral side, making the 

 ventral and transverse diameters near the last septa about as five to eight, some- 

 what obtusely angular on the sides : septa moderately concave, distant on the 

 dorsal side about one-seventh of the transverse diameter, and, on the ventral 

 side, one-seventh of the vertical diameter. Outer chamber short, very gradually 

 expanding. Aperture transverse, subelliptical. 

 All the specimens examined are imperfect casts of the interior; and the only 



evidence of external markings consists of nodes upon the lateral angles, of which 



there is one to about every third septum, with some appearance of arching ridges 



extending from these to the centre of the dorsum. 



This species differs from any other in the Hamilton group, or the Upper Helder- 



berg limestones, by the transversely oval form and closely arranged septa. 



Geological formation and locality. In the Goniatite limestone of the Marcellus 



shale, near Manlius, New- York. 



GYROCERAS LIRATUM (n.s.). 



Shell obliquely subovate; volutions disunited, number unknown, rapidly ex- 

 panding on the last volution. Aperture and outer chamber unknown, the. former 

 apparently subcircular. Septa numerous, a little more straight on the back of the 

 shell, distant from one-fifth to one-fourth the diameter of the shell. Surface 

 marked by strong longitudinal ridges, which, slowly increasing in number, be- 

 come widely divergent towards the aperture, leaving flattened or concave inter- 

 spaces twice or thrice as wide as the ridges. The longitudinal ridges, in the 

 earlier formed portions of the shell, are crossed by strong concentric ridges, 

 which, at their junction, produce nodes. The transverse or concentric ridges like- 

 wise diminish, and become nearly obsolete towards the aperture. There are finer 

 intermediate longitudinal striae, and lamellose striae parallel to the lines of 

 growth. 



The species is described from a fragment of the fossil, with an impression of a 

 larger portion of the same. The fragment is a cast consisting of about twenty cham- 

 bers; and thirteen of these, including what appears to be the outer one, measure 

 upon the back three and one-quarter inches; while the same number, on the curva- 

 ture of the ventral side, measure less than one inch and a half. 



Geological formation and locality. In the Goniatite limestone; at Schoharie, 

 New-York. 



^ GYROCERAS EXPANSUM ? var. 



G. expansum : S^emann, Dunker and Von Meyer, Palseontographica, Vol. iv, 1853, pa. 167, 



pi. 21, f. a, b, c. 



The specimen resembles, in some points, the figure given by S^mann ; but it 

 expands more rapidly, and the volution, in its second turn, is in contact on a few 

 of the last chambers. The ventral side is somewhat flattened, and concave only for 

 a short distance at the junction of the second volution. The transverse diameter, 

 at the ninth septum from the outer one, measures indirect line one inch; while the 

 vertical diameter is a little more than five-eighths of an inch; the septum being about 

 two-fifths of the whole diameter from the ventral side, which is much farther than 

 represented by S^emann in a section of greater diameter. 



The surface is cancellated by fine elevated diverging longitudinal strias, which 

 are crossed by finer closely arranged concentric striae. 



