Figs. 1 and 
Figs. 3 and 
Figs. 4 and 
Fig. 
Figs. 8 and 
Fig. 
9 
a 
a 
w 
for) 
PLATE LY. 
ORTHOCERAS NICOL GETI, eS) -00 OV ri-si\0s eter neteaiceioielsiiciece sion e Rieter 
View of the portion of the conch of the original specimen; showing the strong, 
distant annulations and the obliquity of the septa. x 11-6. 
Outline of a septum; showing the position of the sipho. 
From the Trenton limestone at Belle Creek, Minn. 
ORTHOCHR'AS TOW O RUS wa] aia ereticrsirctarera act tee sote ci ere Takeo poleventel shetatoveratereteiere atevahay steleneiere rales 
A portion of an internal cast referred to this species. 
Outline of septum, showing position of sipho. 
From the Trenton limestone, Minneapolis, Minn. 
ORTHOCERASOLEN DIS DR LAT UM gE o.claretaleiclaselaloveyafaletale erate olatenafelctchateretelitelsiatsfointatalelolaistatete 
A portion of a conch protruding from an internal cast of a Cameroceras-sipho, and 
retaining the surface ornament. x 11-6. 
An enlargement of the surface: showing the fine concentric ines crossed by longi- 
tudinal bands which appear to be traces of color-streaks. Cannon Falls, Minn. 
OREHOCEBASESO OLA TER pe eVal ojo cs ajorelataisnct nia! alets/areverele eferstalerqveretoteleiero cers venerateforene mater statate 
An internal cast apparently entire at the aperture; showing the form of the shell, 
length of the body-chamber and the distances between the septa. 
From the Maquoketa or Hudson River shales at Graf, Iowa. 
ORTHOCHRAS EES UE URE MSD sO Nocimiciee ee isisteleiste istsisvels ateletedeloreinieteliensTe elite (eletsistetsietet-felenemeais 
(See also plate LIII.) 
An internal cast with very regular annulations. Trenton limestone, Dixon, Ill. 
An internal cast having the annulations slightly undulating and the septa lying 
regularly in the intervening furrows. Trenton limestone, Cannon Falls, Minn. 
ORMHOCHRAS BEL DR AMT s SI) sml OVerepeletc atelnirieietelatns cieverereeieleeamticte nel shelelesi eteleletetsin elon eletcter= 
The original specimen, natural size; showing the body-chamber and thirteen septa. 
Galena limestone, Wykoff, Minn, 
789 
785 
