242 
Kirtley F. Mather 
the forms to which those names have been given are conspecific 
with each other and with the material at hand. The reference 
to Orthoceras is believed to be correct, in spite of the rapid 
enlargement of the shell, because of the small siphuncle and 
smooth surface. The type of Geisonoceras, G. rivale (Barrande), 
is characterized by a large siphuncle and banded surface mark- 
ings. 
Horizon and locality. Brentwood limestone: near Fayette- 
ville, Arkansas (Station 135). Morrow formation: near Ft. 
Gibson, Oklahoma (Station 303). 
GL YPHIOCERA TID^ 
Genus GASTRIOCERAS Hyatt 
Gastrioceras branneri Smith 
Plate XVI, figures 12, 12a. 
1896. Gastrioceras branneH. Smith, Proc. Am. Phil. Soc., vol. 35, p. 
257, pi. 23, figs. 1-6. Reprinted 1897 as Cent. No. 9, Hopkins 
Seaside Labor., Leland Stanford Univ. with changed pagination 
(25L-=47). 
Lower Coal Measures: Pilot Mountain, Carroll County, Arkansas. 
1903. Gastrioceras branneri. Smith, Mon., U. S. Geol. Surv., No. 42, 
p. 83, pi. 11, figs. 8-13. 
Chester group. Lower Carboniferous : Pilot Mountain, Carroll 
County, Arkansas. 
1914. Gastrioceras branneri. Smith, Leland Stanford Univ., Publication, 
Acceleration of Development in Fossil Cephalopoda, pi. 1, figs. 
12-14. 
Two specimens of this species, described some years ago by 
Dr. Smith from the Morrow horizon in Carroll County, are in 
the collections at hand. One is a small fragment while the other 
is a more nearly complete shell. The latter, in comparison with 
the figures of the type specimen, appears to be slightly more 
flattened on the venter but in all other respects is identical. 
Horizon and locality. Hale formation. East Mountain, Fay- 
etteville, Arkansas (Station 149). Morrow formation: near Ft. 
Gibson, Oklahoma (Station 296). 
Gastrioceras kesslerense n. sp. 
Plate XVI, figures lO-lOb. 
Description. Shell of medium size, discoidal, with whorls 
slowly increasing in size, depressed semi-circular in cross- 
