PLATE XXVII. 
Zone of Aeffoceras armatum. 
Fig. 1. Aegoceras submuticum, Oppel. Lateral view, natural size, showing the 
regularity of the ribs and sraallness of 
the tubercles ; likewise the small amount 
of the involution of the last whorL My 
collection. 
2. — — — Front view of the siphonal area, showing 
the tubercles in profile, the squareness 
of the siphonal area, and the numerous 
small ridges that cross the area between 
the larger folds. 
