12 EDITOR’S PREFACE. 
less have been some other changes and additions if the author had lived to 
see the work through the press, it is believed that as now published it 
fairly presents his latest views. ‘The illustrations were all made under Pro- 
fessor Hyatt’s supervision, except a few, which were definitely selected and 
indicated by him, and most of which are copies of published figures. He 
had also mounted the figures on the first twenty plates and had written the 
descriptions of nineteen of the plates. The other figures were nearly all 
labeled with specific names. ‘The manuscript was in two packages, one of 
which began with the ‘‘General remarks,” followed by Pulchelliidee, Knemi- 
ceratidee, Engonoceratidee, and Placenticeratidee, which is nearly the 
arrangement of the original manuscript of 1897, while the second package 
began with Mojsisovicsiidee and ended with Coilopoceratidee. The plates 
arranged by the author contain all the illustrations except the Placenticer- 
atidze and a part of the Engonoceratide. By transferring the introductory 
“General remarks” from one package to the other and then uniting the 
two packages the descriptions fell into practically the same arrangement 
that was adopted for the figures, and which evidently represented the 
author’s latest views as to their relationships. The assignment of the fami- 
lies to higher groups was not fully carried out by Professor Hyatt, and it 
is thought best not to attempt to complete it, in view of the fact that his 
opinions as to the definition and limits of the different superfamilies evi- 
dently were much modified, though never formulated, after the publication 
of his chapter on Cephalopoda in Zittel’s Text-book of Paleontology. In 
that work he divides the Ammonoidea into several suborders, and between 
these and the families there is another unnamed category of groups, which 
may be called superfamilies, such as Mammitida, Cosmoceratida, ete, 
Part of the Pseudoceratite families are there referred to Mammitida, part 
to Placenticeratida, the Pulchelliidze were accidentally omitted, and other 
families were not there described. In the present paper a list of the fami- 
lies belonging to the Mammitida is given, but beyond that group the clas- 
sification is doubtful. In connection with the description of Vascoceras, 
Cosmoceratida is mentioned in such a way that the reference of the genus 
to that group may be inferred, and later in the manuscript the heading 
Mantelliceratida is inserted, but there is nothing to warrant the assumption 
