1074 THE PALEONTOLOGY OF MINNESOTA. 



[Oyrtospira tortills. 



genus, but also for the reason that it proves to have been fully established as early 

 as, if not before, the oldest known true Subulites;* also because it continues its 

 peculiarities without material modification, and with no apparent tendency to pass 

 into Subulites, from the base of the Stones River group to or near the top of the 

 Upper Silurian. C. tortilis and C. bicurvata are from the first horizon, C. parvula 

 Billings sp., from the Black River group, C. ivykoffensis and C. abbreviata Hall sp., 

 from the Trenton group, C. notatus Billings sp., from the Anticosti group, and C. 

 brevis Winchell and Marcy sp., and C. ventricosa Hall sp., which may be the same, 

 from the Niagara and Guelph formations. The vertical range indicated by this list 

 of species having the characters required by Cyrtospira is precisely the same as for 

 Subulites. Evidently the two groups of shells existed side by side as parallel but 

 distinct genetic lines. 



CYRTOSPIRA TORTILIS, n. sp. (Ulrich.) 



PLATE LXXXI, FIGS. 24 and 25. 



Shell 22 or 23 mm. in night, about 10 mm. in width, straight on the side of the aperture and strongly 

 curved on the opposite side, consisting of about four gently convex whorls, of which the apical three con- 

 stitute but a small part of the whole shell; apical angle about 52; aperture large, acuminate above, some- 

 what truncated below, widest in the middle, the length equalling about three times the greatest width 

 and about two-thirds of the entire length of shell; columella rather strongly twisted, turning forward in 

 its lower part. 



The large size of the aperture, the strong twist of the columella, obtuse apical angle and slight con- 

 vexity of the whorls, together form a shell that is readily distinguished from all other species referred to 

 the genus. 



4 



Formation and locality. Lower division of the Stones River group, Murfreesboro, Tennessee. 

 Collection. E. O. Ulrich. 



CYRTOSPIRA BICURVATA, n. sp. (Ulrich.) 



PLATE LXXXI, FIGS. 21 and 22. 



This is a more slender shell than C. tortilis and is peculiar in having the apical part turned in the 

 usual direction while the last whorl is curved in the opposite way. The body whorl, as seen in a view of 

 the aperture, tapers very gradually to the lower extremity of the columella. 



Formation and locality. Upper part of Stones River group, High Bridge, Kentucky. 

 Collection. E. O. Ulrich. 



CYRTOSPIRA WYKOFFENSIS, n. sp. 



PLATE LXXXI, FIG. 23. 



Although the apex is broken away in both of the specimens upon which this species is founded, 

 enough remains to satisfy us that it was more acute than in either of the preceding species. The body 

 whorl tapers gradually as in 0. bicurvata, but the curve of the shell Is all in one direction, while we are 

 convinced that the spire consisted of one or two whorls more than we find in that species. 



Formation and locality. Fusispira bed of the Trenton group, Wykoff, Minnesota. 

 Collection. E. O. Ulrich. 



As stated under the description of .S'u7wlffi, S. calciferiu, S. daphne and S. >ycht of Billing*, and S. obesut WhltBeld, 

 which are older than the Stones River group, are not, strictly speaking, good species of SubuiUen. 



