20 PSEUDOCERATITES OF THE CRETACEOUS. 
compared with the Ammonitine of the Jura. All of the forms so far inves- 
tigated, which have more than one principal lateral saddle and lobe, acquire 
these characters a stage earlier than the Jurassic species. They appear, as 
stated above, in the neanic stage and are secondary modifications of the 
outlines of the primitive first laterals of the nepionic stage. 
The same law seems to hold in a modified way for the development of 
an extra number of auxiliary lobes and saddles such as appear in Newmayria, 
but my materials have not enabled me as yet to follow this out. This 
statement appears at first sight to be antagonized by that made with 
reference to the arrested development of the sutures in genera like 
Protengonoceras, Engonoceras, ete., which have undivided or bifid saddles 
and lobes only slightly digitated at their extremities. But it will be shown 
in the generic description of Placenticeras that the arrest of development 
takes effect in these Pseudoceratites of the Cretaceous only after the 
three principal lateral saddles and lobes are formed in the neanic stage. 
Consequently, up to this stage, the development is more complex than im 
the young of Jurassic species or any others which have only one principal 
lateral at the sameage. This statement clears up the extraordinary relations 
of these forms to their apparently more complicated allies of the Jurassic, 
and accounts also for the apparent discrepancy existing between the highly 
involute compressed character of the whorls during the neanic stage and 
the very simple aspect of the lobes and saddles; that such highly involute 
compressed forms in the Jura, usually combined with the development of 
highly complex lobes and saddles, has been recorded by me in other papers 
and by many other writers; consequently, when one meets the Pseudocera- 
tites of the Cretaceous he is apt to imagine them to be what Barrande has 
called ‘‘anachronisms,” and difficult problems for the evolutionist. They 
are unquestionably difficult, but they are no more anachronic than any of 
the forms usually named as having this paradoxical character. ‘They are 
simply excellent examples of arrestation of development taking effect 
locally and upon certain structures. These, if I have rightly understood 
the researches of my deceased friend, Professor Cope, the most brilliant 
investigator and profoundest thinker on evolution that America has pro- 
duced, are good examples of his law of retardation in development, and 
also excellent examples of the different way in which I look upon the same 
phenomena. I have never regarded such cases as examples of a tendency 
