The Genus Nannn, Clarke. — Hyatt. 9 
they are supposed to be when the shell of figure 4 has been 
removed from around the edges. The funnels and remnants 
of the septa are shaded with vertical lines. These disappear 
when they come in contact with the shell and do not pass 
around the venter as in all other endoceratites. The substance 
or filling of the siphon is dotted and the remnants of the 
shell clinging to the venter and surrounding the apex of the 
siphon are not shaded. 
The shell was thick and smooth, externally. The funnels 
on the dorsal and lateral aspects of the siphon were certainly 
present and appeared to form the wall of the siphon as they 
do in Sannionites, Endoceras and Piloceras. i. e., pass from 
one septum to the next, building a single wall. Nevertheless 
the length of the funnels was not actually traced except near 
the septa, and this conclusion, that they actually reach from 
one septum to another is an inference from the structure of 
allied forms of the same group. It is very common to find 
the isolated siphons of this family without the delicate shell 
of the lower parts of the funnels, but with remnants of the 
septa and upper parts of the funnels still attached to the solid 
siphon. 
Vaginoceras [Endoceras) belemnitifornie Holm,* differs 
from Sannionites in having the siphon composed of longer 
funnels. Each septum in forming its funnel passes beyond 
and into the opening of the next funnel and reaches, in many 
cases, to a point opposite the opening of the second funnel 
apicad of its aperture. The wall of the siphon is, in other 
words, everywhere and in all stages later than the nepionic 
stage, double and composed of the apical and oval parts of two 
funnels. The young of Vayinoceras belemnififorme, a» ^gured 
by Holm, is very similar to that of ]}^anno, and filled the apex 
of the shell in the same way. 
Materials for comparing the }'oung of Sannionites and 
JSfanno are wanting at present and, although the adults seem 
to approximate closely, it does not follow that the nepionic 
stages will be similar. There are two specimens in the collec- 
tion of the Museum of Comparative Zoology, Cambridge, Mass., 
which appear to be the young of Sannionites (Cameroceras) 
trento)inense,sp. Conrad, and if so the young of this species 
*Abhandl., Dames et Kayser, III, pi. i. 
