no CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



Genus Glyphioceras Hyatt. 



This genus was established by Hyatt ^ to include Carbon- 

 iferous species with semilunular whorls, usually broad and 

 rather low; with divided ventral lobe, and a pair of angular 

 lateral lobes; with the shell usually smooth, but in some 

 cases with weak umbiHcal ribs; with periodic constrictions 

 or varices. Goniatites crenistria Phillips (considered by 

 many paleontologists as a synonym of G. sphcBrictis Martin, 

 the type of the race of goniatites), was chosen as type of 

 the genus. Glyphioceras was divided into two groups: The 

 first with narrow umbilici, and no umbilical ribs at all, or 

 only very weak ones; to this division belong G. sphcericum 

 Martin, G. crenistria Phillips, and many others. The 

 second group contains species with wider umbilici, and 

 often with strong umbilical ribs; to this group belong G. 

 diadema Goldfuss, and several others. ZitteP emended 

 the genus, and included in it Alilnsteroceras, Nomismoceras, 

 and Homoceras. Karpinsky^ afterward attempted to show 

 that Glyfhioceras and Gastrioceras grade over into each 

 other, and that there is no reason for retaining the two as 

 independent genera. But just this same thing might be 

 said of any two nearly related genera. There is certainly 

 no difficulty in distinguishing typical members of both 

 groups ; and since Gastrioceras is a later branch than Glyph- 

 ioceras, it facilitates phylogenetic study to consider them as 

 distinct. As thus emended and restricted, Glyphioceras 

 contains species from the Carboniferous, ranging from the 

 Waverly horizon, goniatite-beds of Rockford, Indiana, the 

 very base of the system, up into the Permian. 



Little work has been done on the phylogeny of this genus, 

 notwithstanding its importance as the chief member of the 

 Carboniferous ammonoids and the type of the whole race 

 of goniatites. The first observations were made by Hyatt **, 



1 Proc. Boston Soc. Nat. Hist., Vol. XXII, p. 328. 

 ^Handbuch der Pala2ontologie, Abtheil I, Band II, p. 420. 



3 M6ni. Acad. Sci. St. Petersbourg, Tome XXXVII, No. 2. Amnioneen der Artinsk- 

 Stufe, p. 46. 



4 Bull. Mus. Compar. Z06I., Vol. Ill, 1S72, No. 5, PI. II, figs. 3 and 4. 



