EDITOR’S PREFACE. 13 
that the latter term was intended to include Heinziidee, Pulchelliidee, Knemi- 
ceratidze, Engonoceratidze, and Placenticeratidee. In the published work 
above referred to, the two families last named are united with Spheno- 
discidze to form the Placenticeratida, but with the removal of Sphenodis- 
cid to Mammitida it seems probable that the superfamily Placenticeratida 
was abandoned. 
The multiplication of families, genera, and species will be understood 
by all who are acquainted with Professor Hyatt’s habit of attempting to 
express in the terminology every important fact observed in the course 
of his investigations. 
In characteristic fashion the author plunges into the midst of his 
subject, beginning his introduction with a discussion of the sutural details 
of Jurassic ammonites, not tarrying even to define the title of the paper or 
to make a formal statement of the problems involved. In a footnote on 
page 546 of Zittel’s Text-book, where he first used the term Pseudocer- 
atites, he states that it “is a descriptive expression for the Placenticeratida 
and Tissotidze of the Cretaceous, which are morphic equivalents of some 
Triassic genera of the Discocampyli as regards both suture and shell form. 
Their origin is traceable, however, to different groups of the Pachycampyli, 
a suborder which appears to have been initiated in the Jura along with the 
Leptocampyli. It is, therefore, improbable that the Pseudoceratites were 
directly connected with the Triassic Discocampyli.” In a letter written 
December 26, 1901, in response to an inquiry from the Geological Survey 
office, he gives the following somewhat more definite statement of the scope 
and purpose of the present work: “I am at work finishing a ‘Monograph 
of the Pseudoceratites of the Cretacic.’ This is an artificial group, includ- 
ing, for convenience of treatment, all the retrogressive genera of the Cre- 
tacic that have sutures with simple outlines resembling those of Triassic 
cephalopods, formerly included under the name Ceratites. The known 
genera described and figured are Buchiceras, Tissotia and its allies, Sphe- 
nodiscus, Knemiceras, Engonoceras, Placenticeras. The aim of this publi- 
cation is to give as full treatment as possible of the structure and relations 
of these genera, in order to determine as far as practicable to what groups 
among the normal progressive forms they are most nearly related.” 
