PSEUDOCERATITES OF THE CRETACEOUS. 
By AupHeus Hyatt. 
GENERAL REMARKS. 
So far as I have been able to see, either in figures or in specimens, the 
Ammonitine of the Jura have only one large first lateral lobe, even in highly 
involute forms, as demonstrated by the admirable researches of Buckman“ 
upon Hyperlioceras discoidum, subdiscoidum, etc., and the same has been 
shown by Oppel’s figures’ of Newmayria discus, hochstetteri, and aspidoides, 
and Quenstedt in-Amm. truelli,“and the similar hollow-keeled forms alsoin New- 
mayria serrodens (pls. 24, 69), Polyplectus discoides, and capellinus (pl. 53), 
which have a very deeply divided and double first lateral, and in Newmayria 
discus (pl. 57) in which there are apparently two or three principal laterals, but 
in the neanic stage only one bifid first lateral. The Arietidae seem to have 
two principal saddles owing to the great development of first auxiliary, but 
this occurs only in the ephebic stage. Aspidoceras and some forms of other 
genera often have two well-divided principal lateral saddles, but this again 
occurs through the late division of the primitive lateral. 
In fact, it may be confidently stated that in the Jura all of the Ammo- 
nitinze have but one principal lateral saddle throughout the neanic stage, 
and when, as very rarely occurs, two or three principal laterals are either 
apparently or actually developed, they occur as purely secondary, or rather, 
tertiary developmental changes in the ephebic stage. 
This fact is of importance because of its bearing upon the biology of 
Ammonitine in the Cretaceous. With regard to these, it may be stated 
> Pal. Mittheil., pl. 4. 
¢Amm. d. schwib. Jura, pls. 24, 69. 
