782 THE PALEONTOLOGY OF MINNESOTA 



[Aetinoceras beloltense. 



ACTINOCERAS BELOiTENSE Whitfield, 1877. 



PLATE XLVII, FIG. 18. 



Orthoceras (Aetinoceras) beloitense WHITFIELD, 1877. Ann. Rept. State Geol. Wis. for 1877, p. 97. 

 Orthocera( Aetinoceras )beloitf.nse WHITFIELD, 1882. Geology of Wisconsin, vol. iv, p. 226, pi. vm, 

 flg. l;pl.x, flgs. 9, 10. 



Original description: "Shell large and robust, subfusiform, moderately expand- 

 ing to the diameter of about four inches, then more gradually decreasing in size to 

 the aperture. Section oval in all the examples noticed, and usually a little more 

 flattened on one side than on the other, with the siphuncle sub marginal on the 

 flattened side. Septa shallow and not often symmetrically arranged; from seven to 

 eight chambers occupy a length equal to the diameter of the largest of the number 

 measured; toward the outer portion of the shell the septa become more crowded, 

 and just below the outer chamber are sometimes less than half the usual length. 

 Siphuncle large, strongly beaded within the chambers, with an inner core, in the 

 casts, having radiating filaments extending to the center of the bead in each 

 chamber. Surface of the shell unknown." 



This species is represented in the collections by two fragments, one retaining 

 sufficient of the air-chambers to show the characteristic form, and also displaying 

 the relatively small sipho which serves as a distinguishing feature from Aetinoceras 

 bigsbyi Stokes. The casts of the sipho in both specimens show a highly crenulated, 

 gathered and puckered surface for the interior of the siphonal tube (endosiphon) 

 and a series of fine canals connecting with the outer siphonal wall, below the funnel 

 of each septum, and this possibly forming a means of communication between the 

 endosiphon and the air-chambers. Each cast of the endosiphon bears upon the 

 proximal or siphonal side a deep longitudinal groove, representing a prominent 

 ridge on the wall of this tube. 



Formation and locality. In the Trenton limestone at Janesville, Wisconsin. 

 Museum Register, No. 8279. 



ACTINOCERAS REMOTISEPTUM Hall, 1850. 



I'LATE LTV. FIGS. 1-3. 



Ormoceras remotineptum HALL. Third Ann. Rep. N. Y. State Cab. Nat. Hist., p. 173, pi. iv, flg. 3. 



Original description: " Cylindrical, gradually tapering; septa moderately convex, 

 distant half the diameter of the tube; siphuncle excentric, large, swelling moderately 

 between the septa and but slightly contracted at the junction of the septa; character 

 of the external surface unknown. 



