10 TAe American Geologist. July, i895 
has a much smaller neponic siphon than JVanno. The tips are 
decidedly similar in form, but have constrictions showing 
traces of the presence of funnels and septa to within a short 
distance of the apex. The siphon, in other words, is made up 
of funnels even in the nepionic stage. 
Endoceras has siphons with swollen ends that in some spe- 
cies must have nearly filled the tip of the shell, but in other 
species this is not the case. There are similar phenomena in 
Piloceratidae; some genera of this group have siphons as small 
as in Sannionites and compare with typical Piloceras as San- 
nionites compares with Endoceras. 
The large size of the apical part of the siphon which ap- 
proximately fills the the interior of the shell in Nanno caused 
that aiithor to speak of this young shell in an article on 
"Cephalopod Beginnings"* as having a hugh protoconch. This 
view is also held b}^ Holm and others in Europe, and is a nat- 
ural inference from the general aspect of the swollen tip, but 
I held the opposite opinion in several papers before the pub- 
lication of Ford's observations. These showed conclusively 
in Piloceras and Actinoceras, both of which have very large 
siphons in the young, that the apex of the shell had a deep 
cicatrix. This discovery shows clearly that the swollen tip 
of the siphon and shell is not a protoconch in the forms in 
which it occurs, but that the apex of the surrounding shell is 
a true conch, having a cicatrix like that of other nautiloids. 
The view that this swollen apical part of the siphon is a 
protoconch is more likely to be taken in V(iginocer((s and in 
JVanno than in Sannionites. Endoceras or Piloceras. In these 
genera the siphon may or may not have a swollen end and I 
am even doubtful whether the existence of this swollen, si- 
phonal apex in the nepionic stage of the shell may not be a 
matter of individual variation in some species. I am quite 
sure, from the materials now on hand, and from Holm's fig- 
ures of Var/inoceras, that it varies greatly in the same species. 
It is also a fact that when the siphon in this stage is swollen 
in Endoceras tliat it must have very nearly filled the interior 
of the beginning or earlier stages of the shell. 
The septa are, however, traceable in some specimens not- 
withstanding the very narrow space in which they were de- 
*American Geologist, vol. xv, p. 125, Feb., 1895. 
