236 KMHSCOCKKAS. COI50CKUAS. KT< . 



Genus EUDISCOCERAS, llymt. 



'Phis type is distinguished by its discoid t'orin. open umbilicus, 

 nnd :in abdominal keel, bordered by furrows and ridges, tin- 

 latter being interrupted or tubercular ; the young with compar- 

 atively large pihe, "Towing smaller and more rlexuous in the 

 jidult. and finally fading away in the larger half of the bodv- 

 volution. 



K. GAHIU, Meek. IM. lOii. tigs. .V.>7, y'.is. Trias. Nevada. 



Family (' L V DON1TJ 1>.K. Hyatt. (Includes Clydonites, Hauer. 

 and ^ 'm'(n-i'/'(ifi, Hyatt.) 



COROCERAS, Hyatt. The species all have numerous lobes and 

 cells, with smooth sutures, and a larv abdominal lobe: the 

 latter being Tery broad and prominent. The \ are pileately ribbed 

 and very involute ; the umbilicus nearly covered. The month 

 is more or less hooded or constricted. 



C. KLLIPTK i s. H:iuer. T. loi;. liji's. .") ( .) ( .i. i;i)(). Tri.-jssic. I/nU- 

 statt. 



Professor Hyatt remarks that the species included in <'/;/</(>- 

 iiife.s form a heterogeneous asseiiiblauc of diverse types from 

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



Family AR1KTID.K. 



Genus AGASSICKRAS. Hyatt. Voun- (jnite immature and re- 

 markable for the prolonged existence of the goniatitic foi-m 

 which is generally confined to the earliest, staiiv of growth in the 

 Ammonites. The living chambers are <|;iite 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 

 a.dult with the perfect, young of A. nhlu*n* shows, however, that 

 both have similar forms and short living chamber^. 



AtiAssicKKAs Sni'ioNiANi s. d'Orb. T. HIS. 11 gs. r,2'.. r,;JO. 



Family OX VNOTI D.K. Young similar to the group of certain 

 aberrant forms of Arietuhv, but the adult instead of the 

 solid keel of Arietid;e possesses a hollow kei-1. Ill the old. 

 however, this keel entirely disappears, leaving the abdomen 

 rounded and almost, flattened, a transformation entirely dis- 



