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PROCEEDINGS OF THE ACADEMY OF 
nearly as wide as all the others, having a nearly circular section, and pre¬ 
senting on its exterior about five broad longitudinal furrows, covering the 
space from the suture above to the base below ; shell otherwise apparently 
smooth. 
Diameter of last whorl, 1*07 (100) ; height of spire, about -72 (67). 
From the oolitic bed “No. 6,” Burlington, Iowa. “ White Collection” of 
the University of Michigan. 
This species is imperfectly known / though clearly distinct from all other 
species of this age, and hence deserving of notice. It is probable that the 
base is regularly rounded into a broad and deep umbilicus, and that the 
aperture is nearly circular. It calls to mind Euomphalus carinatus, Sow., from 
the “ Aymesbury limestone,” but the sulcations are only half as numerous. 
A similar species exists in Whittlesey’s collection, from “Sheldon’s saw¬ 
mill, Big Brook, Orange, Cuyahoga county, Ohio, below grindstone grit.” 
Pleurotomaria vadosa, Hall, (xiii. Rep. N. Y. Regents, p. 108.) To Prof. 
Hall’s description of this species, founded upon casts, may be added the fol¬ 
lowing observations on the shell: The periphery of the body whorl is flat¬ 
tened into a sharp carina, just above which is another, heavier one, but not 
quite so projecting ; a concave belt separates these from another pair of 
ridges which lie near the suture, and are interrupted by numerous regular 
transverse rugulations rising into minute nodes, on the ridges. 
Collected at Rockford, Indiana, by A. Winchell. 
Straparollus macromphalus, Win. Specimens having twice the diameter 
of the types of the species, showing the tube septate a little more than one 
whorl back from the aperture. One specimen preserving the shell, shows 
that it was marked only by incremental lines.^ 
From bed “ No. 1,’’ and the oolitic layer, “No. 6.” “White Collection ” of 
the University of Michigan. 
Straparollus ammon, White. This Burlington species occurs in the so- 
called millstone grit of Western New York, and was figured as Euomphalus 
depressus , Hall, (Geol. Rep. ivth Dist. New York, p. 291.) 
Orthoceras Indianense, Hall. Collected by A. W., at Alan’s and Ger¬ 
main’s quarries, Hillsdale, and Napoleon Cut, Jackson county, Michigan. 
Nautilus (Trematodiscus) discoidalis? Win. A small fragment from 
Rockford, Indiana, affords strong presumption that this species existed at 
that locality. 
CYRTOCERAS, Goldfuss. 
Cyrtoceras Rockfordense, n. sp. Shell rather large, rapidly expanding, 
especially toward the aperture, apparently forming, in adult age, nearly a 
complete whorl. In some specimens the transverse section is subcircular or 
laterally compressed, in others decidedly elliptic, being flattened dorso-ven- 
trally. The curvature is rapid for a shell of so large size, which renders it 
necessary that the chambers should be about four times as deep on the outer 
as on the inner side of the whorl. Septa deeply and regularly concave ; 
siphon small, situated close to the dorsal side. No surface markings are pre¬ 
served on casts. 
Transverse diameter of the last chamber, in a specimen wholly septate, 
1*86 (100); dorso-ventral diameter, 1-35 (72) ; depth of chamber on the dor¬ 
sal side, -59 (32); on the ventral side, *13 (7); diameter of siphon, *10 (5). 
In another specimen the transverse diameter of a section is 1*60; the dorso- 
ventral diameter, -170. 
Collected by A. Winchell, at Rockford, Indiana. 
It is impossible to affirm that this species did not describe one or more de¬ 
tached volutions. In case such was its character, it must have borne a close 
resemblance to Nautilus cyclostomus (Phillips) de Kon., (Anim. Foss. 553, pi. 
xxv. 1 , a, b ; xlix. 1 , a, b.) 
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