210 
AUG. F. FOERSTE 
11. ENDOCERAS PROTEIFORME HALL 
PLATE XXI, FIGS. 1-3; PLATE XXII, FIGS. 1-3; PLATE XXIII, 
FIGS. 1-3; PLATE XXV, FIG. 2 
Endoceras proteiforme Hall, Pal. New York, vol. 1, 1847, pi. 48, 
fig. 4; pi. 49, 1 a-e 
Selected type (Plate XXI, Fig. 1; Plate XXII, Figs. lA, IB). 
The original of Figure 4 on Plate 48 of the publication cited 
above is selected here as the type of the species. This specimen is 
120 mm. long. It enlarges from a diameter of 45 mm. at the 
lowest well defined camera to 51 mm. at a point 100 mm. farther 
up, or 6 mm. in a length of 100 mm., indicating an apical angle of 
3°. The cross-section is approximately circular; possibly there 
is a little depression dorso-ventrally. The number of camerae 
in a length equal to the diameter of the conch equals 7 along the 
entire length of this specimen. The sutures of the septa are di- 
rectly transverse except along the ventral side of the conch, where 
they curve more or less distinctly downward on approaching the 
median part. The septa curve strongly downward, their con- 
cavity equaling 9 mm. where the diameter of the specimen is 48 
mm. At this point the diameter of the siphuncle is 22 mm. For 
a width of 10 mm. the siphuncle either is in contact with the 
ventral wall of the conch or is but very slightly separated from 
such contact. About 60 mm. farther up, where the diameter of 
the conch is 52 mm., the diameter of the siphuncle is 30 mm. 
Immediately above this part of the specimen there is evidence of 
two endocones, of which the lower one is visible also at the lower 
point where the diameter of the conch is 48 mm. This lower 
endocone is estimated to have an apical angle of about 9°. It is 
evident that the two endocones originated at septa separated by 
an interval of about 7 camerae, or a length equal to the diameter 
of the conch. Both endosiphocones lie on the dorsal side of the 
siphuncle, but this varies in different specimens. 
Other Specimens Figured by Hall. — The specimen^® repre- 
sented by Figure la on Plate 49, accompanying the original de- 
scription by Hall, has the ventral side of the siphuncle exposed 
along a width of 18 mm. ; apparently the exposed part of the si- 
phuncle originally was in contact with the ventral wall of the 
conch. The septal necks are faintly concave in vertical sec- 
tions. Apparently they are only a single camera in length, and 
PI. 21, fig. 2; pi. 22, fig. 2; pi. 23, fig. 2, of this Journal. 
