PLATE XXI 
Fig. 1. Endoceras proteiforme Hall. Ventral side of the conch, show- 
ing downward flexure of the sutures of the septa, the siphuncle, and traces 
of the endocones, both at the top and near the middle of the specimen. 
Same specimen as fig. 4 on pi. 48 of Pal. New York, vol. 1, 1847. See also 
plate XXII, figs. lA, IB. Selected here as type of the species. 
Fig. 2. Endoceras proteiforme Hall. Ventral side of a specimen, show- 
ing the downward curvature of the sutures of the septa, and the concave 
vertical outline of the septal necks of the siphuncle. Same specimen as 
fig. la on plate 49 of Pal. New York, vol. 1, 1847. See also fig 2 on pi. 
XXII, and fig. 2 on pi. XXIII. 
Fig. 3. Endoceras proteiforme Hall. Ventral side of a specimen, show- 
ing the siphuncle. Same specimen as figs, lb, Ic on pi. 49 of Pal. New York, 
vol. 1, 1847. See also figs. lA, IB on pi. XXIII. 
All specimens figured on this plate are from Middleville, New York, in 
the Trenton limestone. 
