43 



first forward curve or saddle and then backward, in a waving line, 

 to an acute point, which is slightly anterior to the second one, 

 where it makes another sharp retral angle and again curves for- 

 ward ,in a waving line, to a level with the anterior part of the 

 first saddle, and then abruptly curves back a short distance and 

 then forward and back, so as to make the summit of this saddle 

 bifid and to form a short, narrow lobe at the periphery, in the 

 middle of the ventral side. There are, therefore, two saddles upon 

 each side of the volution, and a bifid saddle in the middle of the 

 ventral part, and one on each side of it, the latter being the lon- 

 ger ones. The two saddles, on the sides of the ventral margin, 

 extend somewhat anterior to the others. The sinuosities of the 

 septa are best understood by looking at the illustrations, and the 

 use of the words "saddles and lobes," for the purpose of reaching 

 a correct understanding, are of doubtful utility. 



This species is distinguished by its general form, transverse 

 section of the volutions and the peculiar sinuosities of the septa. 



Found by the late Wm. Mc Adams in the Coal Measures in 

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

 F. E. Gurley. 



GONIATITES KANSASENSIS, n. sp. 



Plate V, Fig. 9, lateral view; Fig. 10, surface form of a septum; 

 Fig. 11, ventral view. 



Species medium size, subglobose, volutions very slowly enlarging, 

 and lateral and ventral sides regularly rounded. The number of 

 volutions not known. Transverse sections of a volution concavo- 

 convex and the transverse diameter where our shell is broken off 

 is about three times the dorso-ventral. The transverse diameter 

 diminishes towards the apex more than the dorso-ventral and no 

 doubt increases the proportion toward the body chamber of a 

 mature shell. The last volution encloses all the inner ones and 

 leaves a large open umbilicus. The shell is regularly rounded 

 from the open umbilicus, leaving no distinct lateral sides, and the 

 greater transverse diameter near the abrupt walls of the umbilicus. 

 The air chambers are short and complicated. The outer shell is 

 not preserved in our sp *cimen. 



Each septum is broadly arched forward from the ambilicus and 

 then curved backward in a waving line to an acute point, posterior 

 to the commencement at the umbilicus, where it makes a sharp 

 retral angle and curves forward in a waiving line slightly anterior 

 to the first forward curve or saddle and then backward in a waiv- 



