Fig. 1 
Figs. 2 to 4 
Fig. 5 
Fig. 6 
Figs. 7 to 10 
7 
8 
9 
10 
Fig. 11 
PLATE LVIL. 
TRIPTOCHRAS PIANO CON VW E:XcUiM: EDAU Ee) ete cisteter=tetclvisielitelojetetsials eielerelslsb=[alitalatateieiereteriaterseiate 
(See also plate LVI.) 
A partial internal cast of a large shell. Galena limestone, Hader, Minn. 
TRIPTOCHRAS PLAN ODORS AT UM: VV bE GLC aysrsitetevolercletersterctalcteiisie etelave mretelersisieteretenstetsinie iets 
(See also plate LVI.) 
Three views of an internal cast of the body-chamber. 
Trenton horizon, Minneapolis. 
GONTOCERAS PAINGHIPS) EMA 7 tetevereietetorctatelovorpavaterareiaiaierelare ovetete eie/ereleveiie leretal=iiste oy oraisteternter- Tatars 
A partial internal cast; showing the form and depth of the air-chambers, the size 
of the sipho and the filling of the branches of its internal canal. Trenton 
horizon, Minneapolis. 
GONTOCER/AS (OCCED ENA: BEL alls = tarot eyntev elm jcteisie sieteln aie less make tstete ol ele) aie pobeeloeieistel sini ctebatels stots 
A weathered specimen, showing the double curvature of the septa, the size of the 
lateral flange and of the sipho. Trenton limestone, Dixon, Illinois. 
CLINOCERAS MUMIA FORME Whitfleld. <5 oec reece. tele syeroln alelvieist olefelaforesete olelemte rate isiercieiele 
An internal cast of the body-chamber. 
A nearly entire individual retaining the shell. 
An enlargement of its surface. From the Trenton horizon, locality uncertain. 
An internal cast of a portion of the conch; showing the depth of the air- 
chambers, the position and form of the sipho. x 11-6. 
EOTERIOOERAS  -APER TUM “WiHIbe VEN iegemtetelsetertcletatevercperieieia erie ete ctevotsiatelaietatet=iercteleletsietare 
A view of the best specimen observed, retaining most of the body-chamber and 
eleven air-chambers. Galena limestone, St. Paul, Minn. 
