39 



therefore, five saddles and as many lobes. Four of the saddles 

 are somewhat evenly convex, the middle one is only about two- 

 thirds as high as those adjoining and is abruptly depressed, in 

 the middle part, so as to make it bifid, and form a short narrow 

 lobe in the middle of the ventral side. The illustrations will, at 

 once, give a better idea of the septa than any definition can give. 



This species i.s quite peculiar and is distinguished by the general 

 form of the shell, by the hollow cone-like umbilicus surrounded 

 by the sharp denticulated margin of the last volution, by the six 

 furrows that cross the ventral side of each volution and by the 

 saddles and lobes in the septa. 



Found by the late Wm. McAdams in the Coal Measures of 

 Montgomery county, Illinois, and now in the collection of Wm. 

 F. E. Gurley. 



GONIATITES FULTONENSIS, n. Sp. 



Plate IV, Fig. 15, lateral view; Fig. 16, ventral view; Fig. 17, 

 surface form of a septum. 



Species medium size, subglobose, periphery regularly rounded ; 

 volutions rather rapidly expanding. Transverse section of a volu- 

 tion semi-elliptical, the transverse diameter being a little more 

 than the dorso-ventral. Number of volutions not known. The last 

 volution embraces all the inner ones. Umbilicus small, open but 

 not disclosing the inner volutions. The sides of the volutions are 

 slightly flattened and inclined toward the regularly rounded pe- 

 riphery. The sides of the umbilicus are abrupt, and the greatest 

 transverse diameter of a volution is near the abrupt descent to 

 the umbilical cavity. The external shell of our specimen is not 

 ■ preserved. 



The air chambers are very complicated, of moderate length and 

 do not increase in length with the increasing size of the volu- 

 tions. The septa are close in some places and distant in others, 

 depending upon the peculiar sinuosities. Within the umbilicus 

 there is an angle in each septum in the overlapping part of each 

 outer volution, from which the septum, in a gentle arch, turns 

 over the margin of the umbilicus, and from an obtuse angle, 

 curves forward and back, turning more than a half circle and ex- 

 tending back to an acute and prolonged point from which it takes 

 a retral course and again curves forward beyond the first semi- 

 circular curve, and then back to another prolonged point, where it 

 takes another retral course and again curves forward beyond the 

 second prolonged curve and then back to another acute and pro- 



