2IO The American Geologist: ^p''^'- i^'*^. 
the animal kingdom, bilateral, like a ship. If Orthoceras lived 
at the bottom it could have moved along as Sepia docs, — the 
long conical shell is no proof of the contrary, as such gastro- 
pods as Cerithium and Turritella demonstrate. But it must 
then have had strong motive organs, directed toward the bot- 
tom, and if the shell was external, one would not expect to 
find an apertural plane vertical to the axis of the shell as in 
Orthoceras, but inclining toward the ventral side of the ani- 
mal, as in the gastropods mentioned ; if the shell were wdiol- 
ly internal, or at least on its anterior part, then it would, as 
in Sepia, adapt itself to the bilateral form of the animal, which 
in its turn adapt?^ itself to tlie ism-face. of the sea bottom. A 
conical, cylindrical or sack-shaped body with decided differ- 
entiation of both ends and uniformity in circumference is the 
characteristic form for animals of little motion, in which the 
upper and anterior ends are identical, i.e. for sessile forms, 
as certain infusorians, corals, crinoids, ascidians and cirripeds. 
A decided approach to this body form is, among the living 
cephalopods, found in Octopus, which prefers to sit in cavities 
of the rocky bottom and to extend thence his arms in all di- 
rections in search of prey. Mr. v. Martens stated further that 
the strong development of the calcareous shell in Orthoceras 
certainly argued for a very early sessility in the development 
of the young Orthoceras. The base of attachment may, as in 
Fungidse and oysters, have been a very small stone or snail 
shell ; the smallness of which may have forced the older ortho- 
ceratite to effect its static support by sinking its lower end into 
the soft mud. 
Finally it was pointed out by the same investigator that 
one must not be afrAid to assume within a class of quite uni- 
form internal organization, a very great variety in the exterior 
mode of existence ; the great difference in the external appear- 
ance indicates this distinctly, and it is actually found in many 
classes of animals, as among the gastropods, which are most 
closely related to the cephalopods, and also among the lamel- 
libranchs. 
We hope that these theses will be taken as such by Ameri- 
can paleontologists, i.e. as challenges to a discussion of the 
biologic relations of the groups involved ; and of the orthocer- 
atites in particular. There is no doubt that such a discussion 
