462 WISCONSIN NATURAL HISTORY SURVEY 
shell rapidly enlarges, becoming ventricose, and then more gradually narrows to 
near the aperture, where it flanges out. 
Chamber of habitation large, about one-third the total length of the shell, 
gradually enlarging to the last septum. In all specimens the chamber is concave 
near the aperture, but not in the same degree. No other specimen shows this 
Fic. 3.—Exterior view of a crushed specimen of Gomphoceras wisconsinense N.S., 
with a parasitic growth of coral. The dark band near the top of the specimen is a band 
of pyrite or marcasite which is present on practically all of the specimens a short dis- 
tance above the last septum, the significance of which is not understood. The original 
is from Milwaukee and is now in the Public Museum, Milwaukee. 
character as strongly developed as the one figured (Fig. 1). Diameter of an 
uncrushed specimen about 10.5°™. Apertural margin straight. : 
Air-chambers more than 20, increasing in frequency toward the apex and 
