GASTRIOCERAS. 95 



Gastrioceras montgomeryense ^Miller iuid Gurley. 



PL XVI, figs. 1-2-14. 



lS9t>. (riiniafifci^ in»)if(/o/iieri/t'n.s/K, Miller and (rurl(>v. Hull. Illinois State Mu.s. Nat. 

 Hist. No. 11, p. 3S, PI. IV, rigs. 12-14. 



Shell robust, breadth nearly as great as the diameter; whorls slowly 

 expanding, three times as broad as high, deeply embracing, the outer wliorl 

 being indented to one-half its height by the inner one, but the lunbilical 

 shoulders of the inner whorls are exposed in the deej) funnel-shaped 

 urabilieus. Cross section of whorls depi'essed, trapezoidal, broader than is 

 usual in (iastnoceras. Ventral portion flattened aud broad; umbilical 

 shoulders angular and abrupt, descending stee})ly to the umbilicus, and 

 ornamented with sharply incised ribs or nodes. Umbilicus wide and deep, 

 being one-half of the total diameter of the shell. 



There are six constrictions to a revolution, beginning at the umbilical 

 border, curving abruptly forward on the sides and then backward on the 

 abdomen in a broad, gentle seiies. 



Septa consisting of a pair of narrow tongue-shaped ventral lobes, 

 separated 1)}^ a short siphonal saddle, deeply incised by a secondary notch 

 or lobe; a broad, short, latei'al lobe on the sides halfway between the 

 siphon and the umbilical shoulders. 



This species is most nearly related to Gastrioceras listeri, but is broader 

 in proportion, and also has a greater number of con.strictions to a revolution. 

 The lateral sculpture is slightly coai'ser than on G. listeri. 



Occurrence. — Upper Coal Measures, Montgomery County, 111. Type 

 in the paleontologic collection, Walker Museum, University of Chicago. 



Gastrioceras nolinense Cox. 



PI. V, figs. 8-10. 



1857. Gontiitifis noltnensis, E. T. Cox, Geol. (Surv. Kentucky, Vol. III. p. .574, 



PI. X, figs, i, la, lb. 

 1891. Gonlatltes )wUmii»;.% C. R. Keyes, Proc. Acad. Nat. Sci. Phila., 1891, p. 264. 



Form subglobose, somewhat compressed laterally. Whorls highly 

 arched, with broadly rounded abdomen and slightly flattened sides, deeply 

 embracing, and covering most of the inner volutions. Umbilical shoulders 

 abruptly rounded, umbilicus narrow, being not over one-fifth of the total 



