354 A. Winchell on supposed New Cephalopods. 
Huros: Group,’ 4-004 6a. Oe a TS i ae 210 feet. 
) Shales, limestones and flagstones, .......... 
(hb) Green shalepices VEER, ds eG 1 10 
(a) Black bituminous shales, ..........2-0000s 20 
Hameilion Group, 155 cwcsay gs eines Jason hours ase 55 “ 
The reéxamination of the ferruginous sandstones and under- 
lying shales, which have been made within the last two or three 
Descriptions of Cephalopods from the Marshall and Huron Groups of 
Michigan, 
OrtHoceras InpIANENSE. 
p.. 10h 
Septate portion of shell more than 3°75 inches* in length; 
inclination of sides forming an apical angle which varies 10 dif 
i 6° tol 
and 3:46; ratio of concavity of septum to its diameter 281; . 
ratio of diameter of siphon to diameter of shell 5°67. No sur 
face markings discernable on the cast. 
Localities. The most abundant Orthoceras in the Marshall 
sandstone. I have specimens from Marshall, Calhoun county, 
* The measurements in the following descriptions are all given ininches © 
@ measuremer is followed by a number in parentheses, the latter is the re/atsve 
‘mension, the g patest . in th description being assumed as 100. 
