914 THE PALEONTOLOGY OF MINNESOTA. 



lOxydlscus 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 near 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. E. O. Ulrich. 



OXYDISOUS ORISTATUS Safford. 



PLATE LXXXII, PIGS. 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 0. subacutus Ulrich, yet not strictly identical. The Tennessee species is 

 uniformly larger, the greatest diameter in four specimens varying between 30 and 

 38 mm. 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 0. subacutus as distinct from 0. cristatus. 



Formation and locality. From Safford's "Middle Nashville," which we regard as representing an 

 upper member of the Trenton group, at Nashville and in Jackson county, Tennessee. 



Collections. J. M. Safford; E. O. Ulrich. 



Genus BELLEROPHON, Montfort. 



Bellerophon, MONTFORT, 1808, ConchiliologieSystematique, vol. i,p. 51. WAAGEN, 1880, Pal. Indica, 



ser. 13, pt. 2, pp. 130 and 133. 



Bellerophon (part.), HALL, LINDSTROM, 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 



