914 THE PALEONTOLOGY OF MINNESOTA. 
[Oxydiscus cristatus. 
compared. The Candian species will be found to be more compressed, and to have 
the edge of the umbilicus less abrupt. For comparisons with Safford’s species see 
next description. 
Formation and locality.—Upper beds of the Trenton group pear Danville, Kentucky, where more 
than twenty specimens were obtained. We have reason to believe that the same species occurs also 
in Tennessee and in the Fusispira bed in Minnesota. 
Collection.—K. O. Ulrich. 
Oxypisous cristatus Safford. 
PLATE LXXXII, FIGS. 26—28. 
Cyrtolites cristatus SAFFORD, 1869, Geol. of Tenn., p, 289. 
Through the kindness of Prof. J. M. Safford we have before us the types of his 
Cyrtolites cristatus. These show conclusively that the species is an Oxydiscus, closely 
related to O. subacutus Ulrich, yet not strictly identical. The Tennessee species is 
uniformly larger, the greatest diameter in four specimens varying between 30 and 
38mm. More important differences are (1) that the whorls are one less in number 
in mature examples, (2) that they increase more rapidly in size, (3) that they 
embrace each other in a lesser degree, the amount being in no case more than a 
sixth of the hight of a whorl, while the last may become entirely free, without, 
however, any appreciable diminution in the depth of the sharp furrow, which, 
farther inward, receives the keel of the preceding whorl. In consequence of the 
peculiarities mentioned, the umbilicus is relatively somewhat larger. Finally, the 
shell substance is comparatively thicker on the ventral side, and the keel more 
distinct than in the Kentucky species. Taken all in all, we do not see how we can 
do otherwise than regard O. subacutus as distinct from O. cristatus. 
Formation and locality—From Safford’s ‘‘Middle Nashville,” which we regard as representing an 
upper member of the Trenton group, at Nashviile and in Jackson county, Tennessee. 
Collections.—J. M. Safford; E. O. Ulrich. 
Genus BELLEROPHON, Montfort. 
Bellerophon, MONTFORT, 1808, Conchiliologie Systematique, vol. i, p. 51. WAAGEN, 1880, Pal. Indica, 
ser. 13, pt. 2, pp. 130 and 133. 
Bellerophon (part.), HALL, LoxpsrR6M, and most authors prior to 1880. 
Waagenia, de Koninck, 1882, Ann. Soc. Geol. de Belgique, p. 14. 
Waageniella, BAYLE, 1883. Proposed instead of WAAGENIA which was preoccupied. 
For generic characters and list of species see page 853. 
Adopting this genus in the restricted sense proposed by Waagen, we have an 
easily recognized and still large group of Paleozoic shells. The numerous species 
are of a remarkably uniform type, distinguished at once from Protowarthia by its 
slit-band and different apertural emargination; from Bucania and allied genera by 
