852 THE PALEONTOLOGY OF MINNESOTA. 
[Bellerophontiide. 
subcordiform, widest in the middle or below, without callosities of any kind, nor 
with a sinus in the outer lip. From the aperture to a point about half around the 
dorsal circumference of the last volution there is a narrow open slit lying between 
two sharply elevated edges; behind this point the slit is closed over and forms an 
ordinary slit-band with distinct lunule. Surface with close or distant transverse 
imbricating lamelle, the anterior edges of which are zigzagged and sometimes 
greatly spread out. Lamell plicated, the successive: folds often arranged so as to 
form small revolving ridges; over all very fine lines of growth. Type, C. obliqua 
DGS: 
C. fimbriata U. & S. Stones River group. C. imbricata Meek & Worthen sp. Trenton gr. 
QO. triangularis U. & S. Stones River group. C. elegans Miller. Loraine group. 
C. grandis Ulrich. Stones River group. C. bellula Ulrich. Loraine group. 
C, obliqua U. & S. Black River group. C. dyeri Meek. Richmond group. 
C. compressa Conrad sp. Trenton group. C. dyeri, var. cellulosa U. & S. Trenton. 
C. similis Ulrich. Trenton group. C. pannosa Billings. Hudson River group. 
Oxypiscus, Koken.* (T’ropidodiscus, Meek,y Waagen{, not Steininger, 1855.) 
Strongly compressed, disciform shells; volutions embracing very little, expanding 
gradually to the aperture, sharply keeled; aperture somewhat lanceolate or subtri- 
angular, without an inner callosity; outer lip with a deep V-shaped excision, 
continuing in the dorsal keel as a long and very narrow slit; behind the slit the 
summit of the keel may show a more or less distinct band with lunule, or merely. a 
delicately bordered raised line. Surface markings consisting of growth lines only. 
These bend strongly backward in passing from the ventral side of the whorl to the 
keel. Type, O. ¢mitator Koken. 
AMERIUAN SPECIES. 
O. acutus Sowerby sp. Lower Silurian. O. cristatus Safford sp. Trenton. 
' O. disculus Billingssp. Black Riv. and Trenton. O. magnus Miller sp. Cincinnati. . 
O, subacutus Ulrich. Trenton. O. curvilineatus Conr. sp. Schoharie grit and Up. Held. 
According to Koken Euomphalus strongi Whitfield, a “ Lower Magnesian ” fossil, 
probably belongs here. 
EUROPEAN SPECIES. 
O. (Huomphalus) planissimus Hichwald. Low. Silur. O: (Cyrtolites) orbiculus Lindstrom. Up. Silurian. 
O. (Porcellia) scutigerus Eichw. Upper Silurian. O. (Cyrtolites) delanoniit Giblert. Low. Devonian. 
O. (Cyrtolites) discus Lindstrom. Upper Silurian. O. imitator Koken. Middle Devonian. 
Family BELLEROPHONTIIDA. 
Symmetrically involute shells, the whorls enlarging rapidly, the mouth gener- 
ally expanded laterally and ventrally, not dorsally, the umbilicus mostly small or 
closed. Inner lip more or less thickened, the outer sinuate and centrally emarginate, 
*N.Jarhbuch f. Mineralogie, etc., Beilageband vi, p. 390; 1889, 
+ Proc. Chicago Acad. Sci., vol. i, p. 9; 1866. 
+ Pal. Indi¢a, ser. 13, pt. 2, p. 181; 1880. 
