8 
2'he American Geologist. 
July, 1895 
ly and is somewhat ditt'erent from figure 1, showing consider- 
able variation in the form of the termination of the sheath. 
This is in part due to age, since this is obviously an older 
stage than that given in figure 1. It is probable that Xanno 
aulema was a short shell, all the indications being in favor of 
this opinion. If so the tubular termination of the sheath in 
figure 1, wOiich is undoubtedly ephebic, indicates that the 
more abrupt and stouter termination in figure 3 is a degener- 
ation due to age, and implies that the senile stage had been 
entered upon in this specimen before the animal died. There 
are no definite endocones and the filling is very solid and 
opaque, the radiation of the deposits is also less distinctly 
marked than at younger stages. The lower end of this frag- 
ment of a siphon is swollen slightl}'^ showing that the proxi- 
mal part of the nepionic stage is present and that the distal, 
or younger part, only is missing. The shell is preserved and 
is shown in figure 4 on the ventral side and in figures 5-6. 
These figures demonstrate relations between the siphon and 
shell unparalleled in the history of similar fossils. The shell 
on the venter is in absolute contact with the w^alls of the 
siphon so that it becomes part of the siplional wall on that 
side. Microscopal sections of more perfect specimens are 
needed to establish the details, but so far as can be deter- 
mined by this fossil, it appears to be quite certain, that the 
septa and funnels, which exist on the dorsum of the siphon 
and which there and on the sides form the wall of the siphon, 
have entirely disappeared on the venter. This alone estab- 
lishes Nanno as a new form of the UuJoceratidtt. 
Figure i. 
The shell in the section, figure 3, is the outer or ventral 
wall of the siphon and in the ideal view, figure 1, page 8, 
the relations of the ventral shell to the siphon are shown as 
