CARBONIFEROUS AND PROTOZOIC SPECIES. 



581 



SCAPIIITES (AMMONITES ?) NODOSUS. (N. S.) 

 (Tab. VIII., fig. 4.) 



Specific character. — Shell large* and ponderous. Volution subcylindrical, enlarging gradually towards 

 the terminal chamber. Surface ornamented with sinuous costac, most of which bifurcate at different 

 distances from the umbilicus, and thus multiplied, proceed across the dorsum. Two rows of very promi- 

 nent tubercles. The row near the periphery especially large and prominent, and from one-half to three- 

 quarters of an inch apart. Aperture subovate. Serrations of sutures represented, fig. 4, a. Greatest 

 diameter, four inches ; greatest thickness, two and a half inches. 



It is associated on Sage Creek, a southern tributary of the Cheyenne, with Inocerami of huge dimen- 

 sions, one of which is represented by the medal-ruled plate, Tab. VIII. A. 



GYROCERAS BURLINGTONENSIS. (N. S.) 

 (Tab. V., fig. 10.) 



Specific character. — Scroll-shaped; volutions about two, rapidly enlarging ; chambers forty-eight (?), 

 indicated by undulating lines curving from the inner margin to the periphery. 



This Gi/roceras is of unusually large dimensions, — about fifteen inches in diameter, and nearly three 

 feet along the dorsal circumference of a single coil. It occurs in the oolitic bed, at the top of member a, 

 of the Lower Series of Carboniferous Limestones, under the encrinital beds of the quarries at Burlington, 

 Iowa. 



DISCITES TUBERCULATUS. (N. S.) 

 (Tab. V., fig. 14.) 



Specific character. — In the character of the volutions, general form, and contour of the shell, this fossil 

 resembles Nautilus (^Discitcs) subsulcatus of Phillips, but differs in the back not being concave along the 

 middle, but flat ; also in the presence of a row of tubercles on cither side of the flat dorsal surface ; neither 

 is there any concavity of the sides towards the outer edge. 



Locality. — Towa Point, Missouri River, in carboniferous limestone. 



GASTEROPODA. 



PLEUROTOMARIA MURALIS. (N. S.) 

 (Tab. II., fig. 6.) 



Specific character. — Obtusely conical ; convolutions five to six, with nearly vertical sides, like a spiral 

 wall ; upper surface of the whorls deeply channeled, and doubly carinated ; undulating striae, transverse 

 to the convolutions. Height about two-thirds of the width. 



From the Magnesian Limestones (F. 3) of Red River of the North. 



STRAP AROLL US (EUOMPHALUs) MINNESOTENSIS. (N. S.) 

 (Tab. II., figs. 12, 13.) 



Specific character. — Flatly turreted above, deeply umbilicatcd beneath ; convolutions about three, 

 sharply angular, and carinated around the periphery, with a shallow canal on the upper surface ; aperture 

 small and subrhomboidal ; 1| inches in diameter. 



From the Lower Magnesian Limestone (F. 2), Traverse des Sioux, Minnesota. 



* This is by far the largest boat-shaped concamerated shell that has ever come under my observation. 



