102 PSEUDOCERATITES OF THE CRETACEOUS. 
highly coronate forms like Hrymnoceras in the Inferior Oolite have to true 
Stepheoceras, but until the young are known there can be no certainty in 
such conclusions. 
The similarity of this genus to Olcostephanus is very close indeed. The 
coste on the venter of that genus are, however, not so fold-like, and the nodes 
on the umbilical shoulders are correspondingly smaller and more numerous. 
The sutures in Olcostephanus are much more complex in outline, and there 
are fewer saddles and lobes. 
The coronate form of the volutions and deep open umbilici retained in 
some untuberculated shells have a certain remote resemblance to some 
forms of Pachydiscus, but, so far as | know, none of these, nor any species 
of Cretaceous Ammonitine, have volutions so excessively depressed and so 
similar to the Stepheoceratidse of the Jura:and some Goniatitinze of the 
Carboniferous. 
The living chamber is full three-fourths of a volution in length. Lat- 
eral zones do not exist, the umbilical zones being abrupt and the umbilical 
shoulders on the lateral edges of the venter. 
The only form in the Cretaceous that is similar to this is in the young 
of Gabbioceras batesi (Gabb). This last has a similar coronate form with- 
out any lateral zones throughout the neanie stage, but the sutures show 
this to belong to a different suborder, the Leptocampyli, with which it also 
agrees in the aspect of the shell and the characters of the adults. 
The sutures have very peculiar broad, short ventral lobes and_ first 
lateral lobes. There is but one broad principal lateral saddle, with coarse 
marginal saddles; the lobes and saddles are ammonitic—that is, completely 
margined by small lobes and saddles. White’s figure has the sutures very 
imperfect and much worn away, but shows the orad trend of the auxiliaries. 
It is also defective in regard to the first auxiliary saddle. This is a well- 
defined and very broad saddle, smaller than the first lateral, but otherwise 
resembling it. The sutures are considerably worn away in the specimen 
figured, but the preservation is better than in White’s fossil. The differences 
in the sutures and form from its assumed congeneric associates in the Pul- 
chellidze can be accounted for if it is assumed that this genus is in its 
principal characteristics an arrested development of the coronate form of 
the early stages, as stated in the introduction to this paper. 
