AMERICAN PALEOZOIC CEPHALOPODS 
249 
The siphuncle is almost in contact with the ventral wall of the 
conch; it is moniliform in structure; its maximum diameter 
within the camerae is 2.2 mm., diminishing to 1.5 mm. at its 
passage through the septa. 
Smaller specimen figured by Whitfield. — This specimen (Plate 
XXXVI, Figs. 3 A, B) is illustrated by figures 18 and 19 among 
the series published by Whitfield. It consists of the living 
chamber with 9 camerae still attached. It is closely similar in 
form to the larger specimen figured by Whitfield, but its dorso- 
ventral diameter at the base of the living chamber is only 17 
mm. instead of 22 mm., and its lateral diameter is largest (15.5 
mm.) fully one-third of the height of the living chamber above 
its base, where the diameter is 14.5 mm. The phragmacone ap- 
pears to enlarge more rapidly in size, and the concave curvature 
of the sutures of the septa along the middle of the lateral sides is 
much less conspicuous. On the contrary, these sutures rise 
slightly even along the dorso-lateral sides of the phragmacone 
and their rise is only moderately accentuated along the middle of 
the lateral sides, but they form about the same angle with the 
ventral outline of the phragmacone. In the smaller, as well as 
in the larger specimen here described, the sutures form pro- 
gressively more acute angles on approaching the upper part of 
the phragmacone. 
Phragmacone figured by Whitfield . — This specimen is illus- 
trated by figure 17 of the series published by Whitfield. It 
apparently belonged to a mature individual, judging from the 
distinct shortening of the uppermost camera, compared with the 
camerae immediately beneath. Evidently, even the uppermost 
camera of the phragmacone is preserved. It is significant, there- 
fore, that the dorso-ventral diameter at the top of the specimen 
is only 17 mm., in this respect agreeing more readily with that 
of the smaller specimen figured by Whitfield. The sutures of the 
septa rise even more strongly toward the ventral side of the 
conch. The height of the camerae is distinctly greater, 7 cam- 
erae occurring in a length equal to the dorso-ventral diameter, 
in place of 8, when this length is measured along the ventral side 
of the shell and the dorso-ventral diameter is measured at the 
top of the series of camerae being counted. 
Other specimens . — The Hall collection at the American Mu- 
seum of Natural History includes five specimens in addition to 
