GEOLOGICAL SURVEY OF THE TERRITORIES. 317 



tinct lines of growth, that arch strongly parallel to the margins of the 

 lip, and are crossed on the lower part of the last turn by from three or 

 four to about six distinct, raised revolving lines, and near the middle, 

 especially on those of the spire, by a small nodular carina or ridge. 



Length of a large specimen, about 1.40 inches ; breadth of same, 0.46 

 inch. Angle of spire regular, with a divergence of 18 to 20 degrees. 



The surface markings of this shell, excepting sometimes the lines on 

 the lower part of the last turn, are not seen on internal casts ; while on 

 the exterior, the revolving, slightly-nodular ridge is often obsolete on the 

 last turn, and apparently sometimes nearly or quite so on some of those 

 above. The revolving lines of the under side of the last volution are 

 strongly defined, and it seems to be the upper one of these, continued 

 upon those of the spire, just above the suture, that gives it the banded 

 appearance. In some instances a few smaller revolving lines are seen 

 farther up on the last turn, and even continued upon the lower half of 

 the exposed part of some of those of the spire. Where the nodular ridge 

 is most distinctly developed, the surface of the volutions above it is 

 sometimes slightly concave. 



Professor Hall's figures, especially his Fig. 12 of CeritMum nodu- 

 losum, represent the suture as being more oblique than'in our specimens, 

 but this is probably due to lateral compression. None of his figures 

 show the strongly-arched lines of growth, nor more than one of the 

 revolving lines on the lower part of the last turn. Both are mentioned, 

 however, in his description. The arching character of the lines of growth 

 is a distinctly-marked feature in this shell. 



As the name nodulosa had been used by Dr. Lea for a species now in- 

 cluded in the genus Goniobasis, it becomes necessary to find a new name 

 for the shell under consideration, in placing it in that genus, consequently 

 1 have called it G. nodulifera. 



Locality and position : Colonel Fremont's specimens of this species, 

 according to his observations, came from latitude 41°30 / ; longitude 111° 

 where they were found in a yellowish-gray oolitic limestone. Dr. Hay- 

 den's collections of it came from a locality a short distance farther to the 

 southeast. They are in a yellowish-gray limestone, that sometimes 

 shows a few oolitic grains. Dr. E. Palmer brought specimens of it from 

 White River, still faither southeast in Colorado, in a yellowish, distinctly 

 oolitic matrix. Lower tertiary. 



BYTHINELLA GREGARIA, MEEK. 



Shell small, conoid-subovate, spire rather elevated ; volutions five, 

 rounded, or very convex ; suture strongly impressed ; aperture ovate, 

 or slightly longer than wide, with the upper extremity subangular, and 

 the lower rounded ; inner lip not reflected, and leaving by its side a very 

 small umbilical impression that seems not to perforate the axis. Sur- 

 face smooth, or only showing, under a strong magnifier, very minute 

 lines of growth. 



Length, 0.15 inch; breadth, 0.08 inch ; length of aperture, 0.06 inch; 

 breadth of aperture, scarcely 0.04 inch. 



This little shell so nearly resembles, in form and proportions, the 

 figures of Bythinella tenuipes, of Couper, that it is with some hesitation 

 I have concluded to regard it as a distinct species. As that shell, how- 

 ever, is described as having its suture " slightly impressed," and as being 

 " sub-umbilicated," while that under consideration has its suture very 

 deep, and could not be properly described as even sw&-umbiricated, I do 

 not feel warranted in referring our tertiary form to the existing species. 



