124 The Ottawa Naturalist. [September 



ceras) Beloitcnse'' of Whitfield,* from the Trenton limestone of 

 Wisconsin, which it resembles in some respects, in its more 

 flattened venter, more concavely arched septa in the ventral region, 

 and in its proportionately larger and apparently nummuloidal 

 siphuncle. 



Trochoceras INSIGNE. (Sp. nov.) 



Shell, or rather cast of the interior of the shell, rather large 

 and attaining to a maximum diameter of fully five inches, dextral, 

 and consisting of two slender, closely contiguous volutions that 

 are coiled on very nearly the same plane, and slightly compressed 

 both above and below, so that the outline of a transverse section 

 of the outer volution would be broadly elliptical, with the dorso- 

 ventral diameter a little greater than the lateral. Surface of the 

 test unknown, that of the cast marked by large, transverse rib- 

 like plications, which are moderately prominent on each of the 

 sides, but obsolete on the periphery or venter, — and by very 

 small, acute, thread-like spiral ridges. The transverse plications 

 are rather distant, slightly tiexuous and somewhat sigmoidal on 

 each side of the outer volution, where they are separated by wide 

 and shallowly concave depressions. The small spiral ridges are 

 numerous, comparatively close together, through not very regu- 

 larly disposed, and in one specimen, at least, rather larger 

 and more prominent on the periphery of the outer volution than 

 on its sides. Sutures of the septa concavely arched on both of 

 the sides, where each suture intersects one, or rarely two, of the 

 transverse plications. Shape and position of the siphuncle 

 unknown. 



The first specimen of this shell that the writer had seen was 

 given to the late Chief Justice Wallbridge by a quarry man at 

 Stonewall and presented to the Museum of the Survey by Prof. 

 E. J. Chapman in 1895. The exact locality from which this 

 specimen was obtained was for a long time doubtful, but there 

 is now every reason for believing that it came from the quarries 

 at Stonewall. At any rate, in the fall of 1897, two specimens 



Geology of Wisconsin, Vol. iv, p. 226, pi. 8, fig. i; and pi. 10, figs. 9, and 10. 



