GAyTRlOCERAS. 97 



Gastrioceras planorbiforme Shumarcl. 



1855. Goniatites j)/ano)'f>lfnniii.'<, B. F. Shumard, Geol. Suiv. Missouri, Vol. 11, p. 



208, PI. C, figs*. 11-a-b. 

 1894. Goniatites jAanorhifm-mis, C. R. Keyes, Geol. Surv. Missouri, Vol. V. Pt. II, 



p. 221. 



Shell evolute; whorls depressed, rounded, little embracing, elliptical 

 rather than trapezoidal in cro.ss section. Sides rounding- gently to the 

 abrupt umbilical shoulders, which, however, are not angular. Umbilicus 

 very wide, exposing all the inner whorls, being more than a third of the 

 total diameter. 



Surface ornamented with line imbricating l)ands of growth, bearing 

 very nainute stria?, which are flexuous on the abdomen; one constriction 

 has been observed at about the end of the tiftli revolution. Septa 

 gastrioceran in character, with lobes inclined to be pointed, and broadly 

 rounded saddles. Shumard's type was very small, and these septa are 

 larval in character, so this probably does not represent a mature form, but 

 might be the young of any one of several s})ecies of (rastrioceras. 



Occurrence. — Upper Coal Measures, Kansas City, Dovers Landing, Mo. 



Gastrioceras subcavum Miller and Gurlev. 



PI. XVII, figs. 15-17. 



1896. Goniatites sithcavus, Miller and Gurlev, Bull. Illinois State Mus. Nat. Hist. 

 No. 11, p. 45, PI. V. figs. 15-17. 



This species was first described by Miller and Gurley from the Upper 

 Coal Measures of Montgomery County, 111. The writer has a specimen 

 collected by Dr. N. F. Drake in the Upper Coal Measures, Cisco formation, 

 of Graham, Young County, Tex., about 1,000 feet below the Permian. 



The species resembles Gastrioceras globidoswn, but the whorls are 

 narrower, more depressed, more angular on the umbilical shoulders, and 

 less rounded than on that species. The two agree in the septa and in tlie 

 absence of umbilical ribs. 



The figured specimen is in the paleontologic collection. Walker 

 Museum, University of Chicago (Gui-ley collection). 



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

 Graham, Young County, Tex. 



MON XLII — 02 7 



