Jackcl on Orthoceras. — Rncdemann. 203 
verse sculpture predominates ; among them the apex is com- 
monly broken off; further their pronounced tetramery appears 
to me to throw light upon some hitherto unexplained facts of 
the organization of the cephalopods, such as the possession of 
four gills among the older cephalopods, a condition which, as 
is well known, is eventually lost in this class and yields to 
dibranchy ; and further, upon the remarkable tetramerous cell 
division of the cephalopod embryos. While we have until 
lately, been without any clew to the mode of life of the con- 
ularias and from the external similarity of the shell with that 
of certain pteropods have inferred a pelagic habit for these 
organisms, Ruedemann in Albany, U. S., has made a discov- 
ery, which is most interesting, though little noticed in liter- 
ature, namely a colony of young conularias fastened by a rel- 
atively large, conically attached basal chamber to the sea bot- 
tom or to other objects. (R. Ruedemann. The discovery of a 
■sessile Conularia 15th Ann. Rept. of the N. Y. State Geolo- 
gist. Preliminary partial reports in the American Geolo- 
gist, 1896, xvii, p. 158; xviii, p. 65.) 
"Proceeding from certain ideas 'stated by A. E. Verrill 
(Amer. Jour, of Science, 1896, v. 2. p. 80) Ruedemann has 
"briefly expressed the opinion that the conularias might be the 
ancestors of the cephalopods. To the probable objection that, 
in distinction to the calci-testaceous cephalopods, the conular- 
ias possessed a chitinous skeleton, he points to Chrondro- 
phora with its chitinous skeleton and states in accordance with 
the views of Hyatt and others, that the initial chamber of var- 
ious nautiloids might have been chitinous. In regard to this 
I would remark, that, in my opinion, the shell of the conularias 
did not consist of chitin, but of conchiolin and hence was in 
principle like that of the molusks. Moreover, [as stated by 
Ruedemann,] we find in various phyla of the animal kingdom, 
as Anthozoa, Bryozoa, Brachiopoda, that so-called horny skel- 
etons precede the calcareous. 
"Ruedemann holds the view that the conularias were ses- 
sile only in their youth and later became free, or at least could 
quite likely be so. The acceptation of such a possibility seems 
to me to be essentially a concession to the old view concern- 
ing these forms, and has probably not been confirmed since. 
Besides, this assumption would be opposed by nearly the same 
