CEPHALOPODA. 809 
Oyrtoceras corniculum.] 
Hall, as figured by Whitfield,* but is distinguished from that as from other species 
by the rapid expansion and absence of constriction in the body-chamber. 
Formation and locality.—In the Trenton limestone at Minneapolis. 
Museum Register, No. 5048, 
Cyrtoceras cornicutum Hall, 1862. 
PLATE LIX, FIG. 16. 
Cyrtoceras corniculum HALL, 1862. Rept. Geol. Surv. Wisconsin, p. 41, figs. 1, 2. 
Shell small, slender, with graceful curvature, making less than one volution. 
Surface nearly equally rounded, somewhat broader on the dorsum. Transverse 
section nearly circular. Septa very gently and regularly concave. , Sipho ventral, 
intra-marginal, minute, distant by twice its diameter from the margin. 
There are two specimens of this little species, both preserved as internal casts 
in crystalline calcite. But one shows the character of septum and sipho and neither 
indicates the distance between the air-chambers. Enough, however, is retained of 
the form of the shell and its curvature to show its agreement with this species. 
The larger of the two incomplete examples measures, along the ventral 
curve, 30 mm.; along the dorsal curve, 21 mm. At the distal extremity of the 
specimen which is not far from the apex of the shell, the diameters are 2.5 and 
2mm., while at the proximal extremity the dorso-ventral diameter is 8 mm. and 
the lateral diameter 9 mm. 
Formation and locality.—In the Galena shales, Warsaw, Minnesota. Collection of W. H. Scofield. 
JYRTOCERAS NORWOODI, Sp. nov. 
PLATE LX, FIGS. 7—9. 
The specimen upon which this species is based retains the entire body-chamber 
and six air-chambers. The form of the shell is suberect, gently increasing in con- 
vexity from the base of the specimen to the base of the body-chamber, thence 
gradually contracting to the aperture but forming no distinct constriction. The 
shell is stout, with broad dorsum, broad sides and a somewhat narrowed or laterally 
compressed venter. The transverse section is oval, with diameters as 5 to 6, the 
greater dimension being dorso-ventrally. This diameter at the 7th septum is 26 
mm.; at the aperture 22.5 mm. The sutures are nearly transverse with very low 
and broad lateral lobes, an indistinct dorsal saddle and more conspicuous and 
subacute ventral saddle. Throughout their extent the sutures are minutely un- 
dulated, these undulations being most clearly shown on the sides where the upward 
curves of each seem to coincide with obscure longitudinal ridges on the surface. 
* Geology of Wisconsin, vol. iv, pl. vu, figs. 7—9. 
