441 l'M.VoSTOLOGY OF NEW YORK. 



cellus shale, above the limestone, in the finer shales of the Hamilton group, in 

 Central New York, and in the coarser shales of the group in the neighborhood 

 of Cazenovia. 



Formations and localities. In the Goniatite limestone, near Manlius and Scho- 

 harie, and in the hlack shales above the limestone at the same places ; also in 

 the Hamilton group on the shores of Skaneateles lake, Owasco, Cayuga and 

 Seneca lakes ; at Cazenovia and other places. 



GONIATITES CNIANGULARIS. 



I'l.ATKS I.XXI. ITO. 14; LXXIV, FIG. S. 



(joniatUe* uniangidaris, Conrad. Journ. Acad. Nat. S<i. Pliila., vol. 8, p. 268, pi. 16, fig. 4. 1842. 



Hall: Tlin-teenth Rep. N. Y. State Cab. Nat. Hist., p. its. fig. 6 («*). 1860. 

 " " '• Twenty-seventh Rep. N. Y. State Mus. Nat Hist., p. 136. 1875. 



" . " " " Illustrations of Devonian Fossils : Cephalopoda, pi. 71. 1876. 



Shell depressed, suborbicular, discoid, the transverse and lateral diameters of 

 the original specimen being eight and twenty mm. respectively. Other 

 specimens, referred to the same species, have similar proportions, a larger 

 one being as eighteen to forty-six. The lateral faces are gently convex, a 

 little more rapidly curving toward the outer margin, and the periphery is 

 abruptly rounded. 



Volutions all embraced within the outer one, somewhat gradually increas- 

 ing in the younger shells, and more rapidly expanding as the shell enlarges 

 in growth. The number is probably about four, but no entire exposure has 

 been observed. Umbilicus closed externally, and marked by a distinct, 

 rounded depression. Transverse section semi-elliptical, a little expanding 

 on each side at the base, which is deeply indented by the preceding volution. 

 The enlargement of the volutions in a single turn of the spire, in the septate 

 portion of an incomplete specimen, is as six to eleven and six to twelve, and 

 in a larger individual as twelve to twenty-eight. In one specimen referred 

 to thie species the increase is as nine to fourteen ; and in another specimen, 

 preserving a considerable portion of the chamber of habitation, the increase 

 is about from ten to eighteen mm. 



