126 The Arnerfcrni Geoloijht. February, 18&5 
u writrr is \('ry welcome to nie. Ilie more ;is mv observations of facts are 
not called into (luestioii. If Mr. liatlier's int<'ri)retation of these facets 
(lid'i'rs from my own, it may enabl(> us the sooner to s;et at tiie full si,n- 
niticance of tiiese structures. 
Bather's i)aper, entitled ''Cephalopod Ite^inniuiis, '" andcoxcring some 
seventeen i)a;nes of tlie magazine referred to, is briglit, logical and in- 
cisive. 1 am fully alive to the force of his arguments, wdiich, for such 
readers as may care to follow tliis sul)jecl, may be bricHy summarized 
thus: From the |)rimitive cei.)haloi)od ancestor of "fiir pre-Cambrian 
times" have Ix-en derived along divergent lines the threeorders, Nautil- 
oidea, Ammonoidea and Coleoidea (Bather's term for the Dibranchiata). 
These three may be divided into two grou|)s, one in wdiich the proto- 
conch was always fragile and is altogther lost; these are the Nautiloidea. 
The others had a stronger and calcaret)us protoconch and have retained 
it, eitiier witli the shell coiled about it, or enclosed within secondary 
depositions; the.se are the Ammonoidea and Coleoidea. The observa- 
tions which I have made in the first two of my [)apers militate a.gainst 
this proposition, and have, hence, invited attack; t)ut I cannot help 
feeling that Dr. Bather's argument is rather [)rocruslean inasmuch as 
his division of tlie Cephalopoda based upon the destructibility of the 
protoconch was proposed some years before this later evidence was ad- 
duced. It has been argued by me that the protoconch described in the 
first of my i)ai)ers is that of Orthoceras and that the structure (jf Bactrifcs 
as recounted in my second paper and evinced both in its protoconch and 
the position of its septal funnels distinctly shows its orthoceran affini- 
ties. There are some side lights upon the evidence adduced by me in 
regard to these protoconchs which it will be juM-tinent now to direct 
upon the subject. 
The orthoceran character which, in confirmation of the \ lews of 
some of the older paheontologists who knew nothing of its jjrotoconch, 
I ascribe to Bdctrilex, hinges to some degree ui)on the generic character 
of the i)rotoconch-bearing shell regarded by me as Orthoceras. It has 
been already explained that this little protoconch with the first two 
septa attached, was found in a Devonian limestone (Styliola layer of tlie 
(ienesee shales), that its general aspect, the circular conch, tlie central 
position of the sipho on the last sejjtum (1 have shown that it is lateral 
in BactriteH from the very beginning) and the absence of any deflection of 
the conch as in the Ammonoidea, including even MimdcerdH and Ago/iin- 
titej*, all make for Orthoceran. When my description of this fossil was 
first pr(>|)ared I ventured to ask Prof. Hyatt to examine my observations 
and drawings, feeling that in so doing I took the case directly to the 
court of last resort. It was not the rt// on' ni/t of his observations and 
he certainly expressed himself at first as doubting the pertinence of that 
generic reference, still conceding many of I he orthoceran characters of 
the specim(Mi. His position in regard Id it then was similar to that of 
Bather now, invcjlving even the suggestion that, as it wasijuite palpably 
not the protoconch of a goniatite, it might be that of some otherwise; 
unknown ammonoid genus. This argument is a good one either from 
