794 THE PALEONTOLOGY OF MINNESOTA. 



[Gonioconis 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, subequally 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 East Selkirk, Manitoba. 



Museum Register, No. 8293. 



Family GONIOCERATID^E 



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 mouiliform 

 siphonal beads, perforated with radiating canals. 



GONIOCERAS ANCEPS Hall, 1847. 



PLATE LVII, FIG. 5. 



Gonioceras anceps HALL, 1847. Palaeontology of New York, vol. i, p. 54, pi. xiv, flgs. la-o. 



Original description: "General form elongated, somewhat rapidly tapering 

 from the base, extremely compressed laterally to ward' the extremities, and extended 

 into very acute angles; diameters as 1 to 4 or 1 to 5; septa composed of double [?] 

 l;i.miii;r. 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. Throe specimens in the collections are referable to this species, one from 

 the lower blue beds of the Trenton MTJI-S at Mineral 1'oint, Wisconsin, others from the upper portion of 

 the Trenton limestone at Minneapolis, Minnesota. The Now York specimen* aruJrom the Black River 

 limestone at Wati-rtown. 



Ma a- n,u Register, Nos. 5113, 5680, 8208. 



