132 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 carinaius, Sow., from 

 the " Aymesbuty 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, -5;i (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 Nuvtilus cyelostomus (Phillips) de Kon., (Anim. Foss. 553, pi. 

 xxv. 1, a, b ; xlix 1, a, b.) 



[July 



