Figs. 1 to 4 
Figs. 5 and 6 
Figs. 7 to 9 
Fig. 10 
Figs. 11 and 12 
Figs. 13 to 15 
PLATE Lx. 
CYRTOCERAS  SHUMARDIT, (Spy sO ersterererererersverc leer sicleuedelobe aleloteteatelisYoreteiielate late erst-atetarets teeters 
Dorsal, lateral, ventral and septal views of the typical specimen; showing its 
robust form, broad venter, outline and convexity of septum and position of 
sipho. Trenton limestone, Cannon Falls, Minn. 
GYRTOCERAS=CAMURUM EVally ces cnteicre cle stemieite olclete oloialetisetetereyclevere elel=ferete\esevaltfaictefet=teneiet= 
Lateral and ventral views of two fragments believed to belong together and 
drawn as one. The lower portion shows the position of the sipho and the 
narrowing of the conch is due to compression. 
CY RTOCERAS NORWOOD 'SP:) 10 Versein)- 1 evrctetctopectetelereierotelelete ic orele ate ore lalate i ere ete iste sees terete 
Lateral, ventral and dorsal views of a specimen showing the body-chamber, with 
a number of very narrow air-chambers, the fine undulation of the sutures, 
position of sipho, broad and obscure longitudinal bands and the almost impal- 
pable incurvature of the conch. In the Trenton limestone at Rockton, Minn. 
CY RTOCHRASTBLLLENGSI: SALGELs «,.sie's, a0 cj« 2 cers esie,o/els,s)= on om elesaiernie visi eieteielel ale iteoanisyotaneteiees 
A portion of a shell showing the finely and sharply lineate exterior of the conch. 
Trenton limestone, near Cannon Falls, Minn. 
CYERTOGERAS HALDTANUM “DiOTDIGMY:-s <i) <jsastsiateficr ccd ase cieisteineeiaceetieceieen Dien 
Lateral views of a specimen, showing the undulating lamella and some of the 
septa. From the Trenton limestone at Janesville, Wisconsin. 
ONCOOBRASSDOUGIASST ISD eT O Vice viatoccic’s cm: atetritauelaleersiet lores tarsvere ay deve tee eyotaittie eee eleroeieiete 
Lateral, ventral and dorsal views; showing the rapidly expanding conch and the 
contracted body-chamber. These figures are not wholly satisfactory, fig. 13 
being slightly oblique in position and not affording an exact profile; the lower 
septa in figs. 14 and 15 are too oblique. From the Galena beds at Holder, Minn. 
805 
809 
806 
805 
801 
