862 THE PALEONTOLOGY OF MINNESOTA. 
[Cyrtolites retrorsus. 
specimens referred to C. ornatus by Prof. Safford. If any are in doubt, then it is 
those which he obtained from his “Orthis bed,’”’ which, like the Clitambonites bed in 
Minnesota, we place at the base of the Trenton group. The same form occurs also 
in equivalent strata in Kentucky, but none of the specimens seen by us are suffici- 
ently perfect to permit of a positive decision in the matter. So far as the form of 
the shell and volutions is concerned, the specimens in question certainly agree very 
closely with C. retrorsus, and, if appearances are not deceptive, they are like it also 
in the backward swing of the surface markings. The evidence at hand, therefore, 
seems to indicate that all of the Tennessee and Kentucky Trenton specimens 
hitherto referred to Cyrtolites ornatus really belong to C. retrorsus. 
Formation and locality.—Upper part of the Trenton group between Burgin and Danville, Kentucky, 
and Nashville, Tennessee. Probably also in the lower part of the group near the same localities. About 
ten specimens, mostly casts of the interior, have been found by one of the authors in the upper part of 
the Trenton group and in the lower part of the Utica group at Cincinnati, Ohio, and at Covington and 
Newport in Kentucky. 
Collections.—E. O. Ulrich; Prof. J. M. Safford. 
CYRTOLITES RETRORSUS, Var. FILLMORENSIS, 7. var. 
PLATE LXII, FIGS. 38 and 39. 
Under this name we propose arranging provisionally a form occurring not very 
rarely in the shales of the Black River group at localities in Fillmore county. 
Unfortunately, none of the specimens before us are in a good state of preservation, 
all excepting three being more or less distorted casts of the interior. On two of the 
excepted specimens the shell is preserved on the inner volutions only, while the 
the third retains a few lines near the aperture. So far as can be determined, the 
variety differs from the typical form of the species only in having the sides of the 
inner volutions almost rounded, the form of the outer volution and the surface 
ornamentation being apparently as in C. retrorsus. The rounded character of the 
sides of the inner volutions in this, the oldest known variety of the genus, is a 
noteworthy feature, since it may give us a clue to the origin of the genus. 
Formation and locality—Black River group, Ctenodonta bed, Chatfield and near Fountain, Minnesota. 
Collections.—Geological and Natural History Survey of Minnesota; E. O. Ulrich. 
Museum Register, Nos. 4051, 7535, 
CyRTOLITES CARINATUS Miller. 
PLATE LXII, FIGS. 50—52. 
Cyrtolites carinatus MILLER, 1874, Cin. Quar. Jour. Sci., vol. i, p. 311, fig. 32. 
Comp. Cyrtolites conradi HALL, 1862, Geol. Rep. Wis., p. 55. (Figured only.) 
Smaller than C. ornatus, the size being about as in C. retrorsus, the average 
diameter about 13 mm.; in two of our specimens it exceeds 20 mm. Sides sharply 
