2'2-2 MKKKOCKI; \<. t i. v i .< .\ i TKS. < RIOCERA8. 



the yonnm. the characteristics of the superior lateral cells, which 

 :nv invariably divided. MS are those of .-ill the Ammonites proper. 

 Mild also in tin 1 tendency of the yonnm sutures of llm-hirt'rna 

 bilobatii in to assume M wholly Mmmonitic Mspcct. r riie truly am- 

 monitic outline of the cells MIK! lolics in Hur/i /Vr/Y/s title, i iiai u m 

 shows how easily the outlines of the typical divided cells a re 

 transformed into those of M true Ammonite by a few (limitations, 

 whereas the same (limitations applied to the entire outlines of a 

 true CfTfiftfr would produce only a Ceratite. not an Ammonite. 



(iriius MEEKOCERAS. llyutt. 



hislinmiiished from Crra/i/rs by havinm 1( nt three distinct 

 lateral cells and two lateral loles. besides the liner auxiliary 

 loin's and cells. The typical Ceratifrx have at least four distinct 

 lateral cells ami lobes besides i he anxilia ry ones, and the dis- 

 tinction is slio-ht between the two series: in this m<'iius. <>n tin- 

 contrary, the auxiliary series, when present, is not divided from 

 the third lateral cell by a distinct lobe, as in ( V/Y////VS, ;m d the 

 aspect of the third lateral cell is often like that of a Goitinliti'*. 

 The compressed whorls of al' the species is of course a charac- 

 teristic which is obvious when they are contrasted with typical 

 Ceraf/fr.^. as is also the absence, or merely transient appearance, 

 of heavy nodes and rib-,, except perhaps in the least involute 



species. 



Jurassic to Triassic. S. E. Idaho. 



< ;<mi< CLYDONITES, Hau.-r. 



Shell spiral, discoidal. whorls involute: sutures simply lobcd. 

 1 he lobes pointed. 



Twenty-one species. I'pper Triassic. /-;///V/M-. //itiK/lfii/ax. 



Two species. I'pper Cretaceous (described by d'Orli. a- 

 t'rrfilili:*). Ditlerence from Ceral-itr* is the lobes beinm simple, 

 not crenulated. 

 ( . . 08TAT1 8, llaner. PI. 1(MI. lim- :")^0. 



C. DKI.IMIINoi KIMIAU S. Ilaiier. Tl. 10(1. \\^. f>21. 

 (J.-iius CRIOCERAS, Lcv<-illc. 



Shell discoidal. spiral : wlmrN separate : llu-s foliated. 

 Thirteen species. Neoconiian to I". (Jrecnsand. l^nr<>i>r. 

 Some of the Species have been a-ce!lained to be merely in- 



