GOMATITES. 67 



to species of the type of G. spharicus, G. crenistria, and G. striatus; and to 

 restrict Glyphioceras to the type of G. diadema. 



As thus restricted, Goniafifes is ahnost entirely confined to the Lower 

 Carboniferous zone of Goniatltes striatus, and is thus of great importance in 

 stratigra|)hic paleontology. It has been shown by researches in the ontog- 

 eny of Goniatites crenistria"' and Ghjiyliioceras diadema'' that these two genera 

 have a common origin in Prionoceras, which is considered by most paleon- 

 tologists as a synonym of Brancoceras Hyatt, or Afjanides de Montfort. 



F. Freeh *■ thinks that Goniatites s. str. was derived from Sporadoceras ; 

 and certainly *S'. mammlllifenim Sandberger and 8. suhinvolutmn Mueuster, 

 as figured by Freeh, do resemble closely what the writer has described as 

 the Prionoceras stage of growth in Goniatites. It is, however, by no means 

 certain that these species should be assigned to Sporadoceras, as Hyatt took 

 Goniatites mammillifer as the type of his genus Bimeroceras, and regarded 

 it as transitional from Brancoceras to Perici/clus. But if these species should 

 be accepted as genuine members of Sporadoceras, the writer agrees with 

 Freeh in regarding this genus as the ancestral stock of the Glyjjhiocera- 

 tidse s. str. 



Goniatites choctawensis Shumard. 



1868. Goniatites choctawensis,'B. F. Shumard, Trans. St. Loui.s Acad. Sci., Vol. II, 

 p. 109. 



The following description is quoted from Shumard's paper: 



Shell discoidal, broadly and strongly rounded on the dorsum [abdomen] and 

 flattened lateralh', inner volutions entirely concealed by the outer one; umbilicus 

 small, its diameter scarcely equal to one-sixth the breadth of the volution; transverse 

 diameter of volution about equal to the breadth from dorsal to ventral side; 

 aperture lunate, much wider than high; surface marked with tine distinct revolving 

 lines, less than the width of the intervals between, crossed by extremely fine, 

 crowded, transverse striae. Sepfx having but one lateral lobe on either side; dorsal 

 [ventral] lobe as wide as long, divided into two lanceolate branches by an accessory 

 saddle, which is truncated and l)ifid at tip and extends almost to the middle of 

 the lobe; dorsal [ventral] saddle of the same form, but wider and double the length 

 of the brandies of the dorsal [ventral] lobe; superior lateral lobe wider than the 

 dorsal [ventral] saddle, and contracted at extremity to an acute point. 



This shell resembles the G. striatus (Sowerby) both in the form and number of 

 the lobes of the septaj and its surface markings, and for several years I have had 



« J. P. Smith, Proc. Cal. Acad. Sci., 3d series, Geology, Vol. I, No. 3, pjj. 105, 128. 

 »W. Branco, Palieontographica, Vol. XXVII, PI. IV, figs. 1 a-o. 

 ^ Ueber devonische Ammoneen, p. 84. 



