PLATE LIV. 
Figs. 1 to 3 ACTINOCERAS REMOTISEPTUM Hall....................0+- rahe) a (a oietatevajovsletstenere tetra tena 782 
1 Outline of a large example. 
2 The form of the transverse section. 
3 The first two air-chambers, longitudinally sectioned; showing the bulbs of the 
sipho, their thickened walls and endosiphon with its ramifying branches. 
x11-6. From the Trenton limestone at Cannon Falls, Minn. 
Kigs, 4 .and 5 ORTHOCERAS -PERRODI, ISP iO Vere ceie cess c/o ac ae icla lesion clean este ieielenereeiecioereeee 785 
4 A view of a silicified shell, showing the closely annulated exterior and the strong 
alternating vertical strix. 
5 Transverse section at the terminal septum. 
Bigs, “6:and i ORTHOCERAS “BILIN HAT UMaEL al Ueemteeieseyetemtelacesisrrsts lc ieic cieisisreis « ecoetuereierein cee eerie hietats 786 
(See also plate xtvm.) 
6 ‘View of an internal cast showing the relations of annulations and septa. 
7 Another specimen illustrating the same features. 
From the Trenton shales at Minneapolis. 
