stanton.] TURRITELLID.E. 131 



These differences are sufficient basis for the separation of the two 

 forms, and the additional fact that one of them occurs near the base 

 of the Upper Cretaceous, while the other is found at the very top of 

 the Cretaceous — or in the Eocene — makes their separation still more 

 reasonable. 



It should be stated that the specimens from Colorado do not quite 

 agree in ornamentation with those from Utah. The revolving lines are 

 somewhat broader and fewer in number, usually not more than five or 

 six prominent ones, and the intermediate fine thread-like lines are often 

 obsolete. Perhaps such differences are of specific importance, but it 

 seems to me more probable that they are only local variations of one 

 species. If it should ever be found desirable to separate them the Utah 

 form must be regarded as the type of Turritella whitei. 



At a locality about 12 miles east of Walsenburg a number of speci- 

 mens of the Colorado variety were found in a peculiar state of preser- 

 vation that gives them a very different aspect. The shell is entirely 

 replaced by calcite and the surface is eroded until there is hardly a 

 trace of the natural ornamentation remaining. The planing down of 

 the rounded whorls has left irregular zigzag lines that are, in some 

 cases at least, coincident with the angles of the calcite crystals. One 

 of these is figured. 



Locality and position, — About 350 feet above the base of the Cre- 

 taceous section in Upper Kanab valley, Utah; in the Pugnellus sand- 

 stone of Huerfano park, Colorado, and at about the same or a little 

 lower horizon in the Benton shales on the Arkansas river above Pueblo, 

 at Eattlesnake butte, and other places in southern Colorado. 



Turritella micronema Meek. 



PI. xxix, Fig. 3. 



Turritella (Aclis ?) micronema Meek, 1873, Ann. Rept. U. S. Geol. Sur. Terr, for 1872, p. 

 504; White, 1879, idem for 1877, p. 316, PI. 9, Fig. 8a. 



Original description: 



" Shell small, terete or elongate-conical; volutions about nine, nearly 

 flat, sometimes moderately convex, increasing gradually in size, last 

 one rounded or obscurely subangular in the middle; suture linear to 

 moderately distinct; aperture rhombic-ovate, angular above. Surface 

 ornamented by fine, regular, rather crowded revolving lines, six or 

 eight of which may be counted on each volution of the spire. 



" Length of the largest specimen seen, 0.50 inch; breadth, 0.18 inch; 

 angle of spire, about 19°, with slightly convex slopes. [Specimens 

 since found at the original locality, and in the same layers, indicate a 

 size nearly twice as great as this.] 



" This may not be a Turritella, the specimen not being in a condition 

 to show the texture of the shell or to give a clear idea of its aperture 

 and lip. It would be a rather small species for that genus, and if it 



