794 THE PALEONTOLOGY OF MINNESOTA. 
[Gonioceras anceps. 
side. Minor and major diameters of the septa as 1 to 4. Average depth of the air- 
chambers toward the aperture, 6 mm. 
A specimen measuring 90 mm. in length has an upper width of 95 mm.,, a 
diameter at the lower end of 80 mm. and bears thirteen septa. A much larger 
example has a length of 195 mm., of which 45 mm. belong to the aperture and the 
remainder bears seventeen septa. 
The sipho is distinctly ventral and moniliform. Nothing is retained of the 
external ornament. 
This species is readily distinguished by its great size, subequa!ly convex sides 
and the deep concavity of the septa. 
Formation and locality.—The two specimens observed are from the middle portion of the Galena 
limestone at Stewartsville, Minnesota. The specimens described by Whiteaves were from the Trenton 
series at Hast Selkirk, Manitoba. 
Museum Register, No. 8293. 
Family GONIOCERATIDA 
Genus GONIOCERAS Hall, 1847. 
Broad, flat, straight shells, extremely compressed dorso-ventrally, and with 
extended lateral flanges into which the septa are continued. The shells are sub- 
equally biconvex with regularly concave dorsal and ventral lobes, large moniliform 
siphonal beads, perforated with radiating canals. 
Gonrocreras ANcEPS Hall, 1847. 
PLATE LVII, FIG. 5. 
Gonioceras anceps HALL, 1847. Paleontology of New York, vol. i, p. 54, pl. xiv, figs, la-o. 
Original description: “General form elongated, somewhat rapidly tapering 
from the base, extremely compressed laterally toward the extremities, and extended 
into very acute angles; diameters as | to 4 or 1 to 5; septa composed of double [?] 
laminz, deeply concave in the center, numerous, thin, approximate, sinuous on the 
longest diameter; siphuncle moniliform, ventral, consisting of a rounded tube which 
is exceedingly expanded between the septa, like the siphuncle of Ormoceras.” 'To 
this may be added that the septa are moderately distant, the dorsal and ventral 
saddles subacute, the recurvature of the septa of the lateral expansion being in a 
broad curve. 
Formation and locality.—Three specimens in the collections are referable to this species, one from 
the lower blue beds of the Trenton series at Mineral Point, Wisconsin, others from the upper portion of 
the Trenton limestone at Minneapolis, Minnesota. The New York specimens are from the Black River 
limestone at Watertown. 
Museum Register, Nos. 5113, 5680, 8298. 
