AMERICAN PALEOZOIC CEPHALOPODS 
263 
least in southwestern Ohio. Gomphoceras eos and Gomphoceras 
obesum are congeneric. Poterioceras apertum Whiteaves, P. 
nobile Whiteaves, and possibly P. gracile Whiteaves, also belong 
here. Oncoceras alceus Hall is another species. 
51. DIESTOCERAS INDIANENSE (MILLER AND FABER) 
PLATE XXV, PIGS. lA, B; PLATE XXVI, FIGS. lA, B, 2A, B; 
PLATE XXVII, FIG. 2 
Gomphoceras indianense Miller and Faber, Jour. Cincinnati Soc. 
Nat. Hist., vol. 17, 1894, p. 137, pi. 7, figs. 3-5 
Type. — Three specimens were collected by Faber in the upper 
part of the Richmond at Versailles, Indiana, and one was figured. 
The siphuncle was described as marginal, located on the ventral 
side of the conch, and abruptly expanded within the camerae 
to two and a half or three times its diameter at the septa. 
Oxford specimens . — Conch (Plate XXV, Figs. lA, B) rela- 
tively short, rapidly expanding along the lower part of the phrag- 
macone, attaining its largest diameter at the base of the living 
chamber, distinctly contracting toward the aperture. In speci- 
mens retaining about 10 of the upper camerae of the phragma- 
cone, the total length of these camerae along the dorsal side of 
the conch is a little greater than their total length along the ven- 
tral side, and the sutures of the septa rise slightly higher along 
the dorsal side, especially toward the living chamber. The ver- 
tical axis of the conch is nearly straight, but there is a faint ten- 
dency toward a lengthwise concave curvature along the ventral 
side. From this it is assumed that the location of the siphuncle 
is endogastric. The conch is slightly compressed laterally. In 
the specimen which seems least flattened by lateral pressure, the 
dorso-ventral diameter at the base of the living chamber is 
63 mm., and the lateral diameter is 58 mm. At the base of the 
specimen, 46 mm. farther down, the cross-section is virtually cir- 
cular, and about 34 mm. in diameter. Two very short camerae 
at the top of the phragmacone indicate that this specimen had 
reached full maturity. The living chamber is 38 mm. in height. 
The margin of the aperture is nearly directly transverse on its 
dorsal and lateral sides, but curves distinctly downward ven- 
trally, forming a relatively shallow V-shaped hyponomic sinus. 
Possibly the margin of this aperture inclines slightly downward 
toward the dorsal side also, but this cannot be determined def- 
initely from the specimen at hand. The lateral diameter of the 
