336 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



the lowest revolving ridge on each turn, and the highest one on the next 

 below ; marks of growth very fine, regularly-disposed, elevated hair-lines, 

 F'S- 38. much more distinct in the furrows than on the revolving 



ridges, all making a rather deep, graceful, backward curve 

 in crossing the outer flattened sides of the volutions, and an 

 equally distinct forward curve on the lower side of the body- 

 volution below its angle, thus indicating a broadly-sinuous 

 outline for the outer lip above, and an equally prominent 

 outline below the angle of the last turn ; aperture subquadran- 

 CeritMopsis iioreau- gular, with the canal at its lower inner angle very narrow and 

 oblique; columella twisted, and bearing a very distinct, 



Enlarged about 



three diameters, to prominent, rounded plait on its oblique lower edge, and faint 



show tbe little ridge , p , i n , 1 



. t , , e traces of one or two much smaller ones lust above. 



seen at the base of •> 



the columella. Length, about 0.47 inch ; breadth, 0.15 inch ; slopes of 



spire straight, with a divergence of about 9°. 



In form and surface-markings, this little shell has exactly the appear- 

 ance of a Turritclla, to which genus we referred it before seeing any speci- 

 mens giving a correct idea of the nature of its aperture. On subsequently 

 seeing the specimen represented by figure 4 of our plate, it became evident 

 that there is a little canal at the inner lower angle of the mouth, though the 

 lower part of the lip and a portion of the columella being partly broken away, 

 the exact appearance of the parts could not be made out. It showed enough 

 of the characters of the aperture, however, to render it very clear that the 

 shell is certainly not a Turritella; and from its general appearance we were 

 led to refer it provisionally to the genus Cerithiopsis. Another specimen, 

 since brought in, although not showing the aperture, has one side of one of 

 the lower volutions broken away, and thus shows that there is a prominent 

 oblique ridge just at the lower edge of the columella, and faint traces of one 

 or two more much smaller ones just above, as we see in some of the Paris- 

 basin species of Ceriihium. Consequently, it is possible that I would be 

 nearer right to call it Cerithium Morecuiense. After seeing the ridge at the 

 base of the columella of the broken specimen mentioned above, the one 

 figured on the plate was more carefully examined and a little more developed, 

 when the little ridge was also found to exist in it, as shown in the foregoing 

 enlarged wood cut. 



Specifically, this little shell may be compared with such forms as Ceri- 



