236 Kl lIs< orKMAS, CoKiirKK As. KTi . 



EUDISCOCERAS, 



This type is distinguished by its diseoid form. open uinl)iliciis. 

 :uid .-in abdominal keel. bordered by furrows and ridges, the 

 latter being interrupted or tubercular ; the young with compar- 

 atively large pila-, growing smaller and more flexuous in the 

 adult, and finally ftuling away in the larger half of the body- 

 volntion. 



K. G.\I;I;I. Meek. PI. lor., figs. .V.I7, 51)8. Trias. Nevada. 



Family CLYJM >MTI IU-:. Hyatt. (Includes Cli/Amit*-*. Hauer. 

 and Coroceras, Hyatt.) 



<'OROCERAS, Hyatt. The species all have numerous lobes and 

 ells. with smooth sutures, and a large abdominal lobe ; the 

 latter being very broad and prominent. They are pileately ribbed 

 and very involute ; the umbilicus nearly covered. The mouth 

 is more or less hooded or constricted. 



C. ELLIPTICUS, Hauer. T. 1(K. tigs. .V.i'.i. C,(K). Trinssie. llull- 

 xtatt. 



l'r<tr oi- Hyatt remarks that the species included in Ch/do- 

 nt/<'tt form a heterogeneous assemblage of diverse types from 

 which it will be necessary to eliminate other new generic groups. 



Family ARIKTIh.K. 



Genus AGASSH-.KRAS. Hyatt. Young <|iiitc immature and re- 

 markable for the prolonged existence of the goniatitic form 

 which is generally confined to the earliest stage of growth in the 

 Ammonites. The living chambers are quite short, the abdomen 

 keeled, but not channeled. This genus would not be placed in 

 the group of Arietida- by many authors. A comparison of the 

 adult with the per fed young of .1. thftixti* shows, however, that 

 both have similar forms and short living chambers. 



AOAKSICERAS SciPiONiAM s. d'Orb. T. los. ligs. r,iM. f)30. 



Family O\ Y NOT I D.K. Young similar to the group of certain 

 aberrant forms of Arietidte, but the adult instead of the 

 solid keel of Arietidse pOe0688eS a hollow keel. Ill the old. 

 however, this keel entirely disappears, leaving the abdomen 

 rounded and almost, tlattened, ;) transformation entirely dis- 



