olU'KK II 



A.M.MoNOIhKA 





iii primiti'. .ml are more or lea traceable even in specialised -helk 



Aperture with hyponomic, .-imis. Shell.- .-mooth or willi lougitndin .. 



Example- : l>i,,t,,i-jiln,<; /-,(>, \,,iiii'*i,>'.' < . 1 1 \. tit. ( 'arbonifi-roii-. 



Family "). Thalassoceratidae. l>i-roidal and involute ammoniticone- uit'n 

 undivided ventral lobes in primit ivr form.-, and al-o cut in- lob,- and .-addle-; l.ut in 



more specialised slid is tin- former are divided j and tin- latter digitated by marginal-, 



1 nit bases of saddle- may remain entire. ( )iit liiu-s of -ut lire- in primitive form- indicate 

 affinity with XIHIU'IIHH-I-I;I.<, and probable derivation from -aim- >tork. Apertniv with 

 liyponoinie sinus. Shells smooth. 



Examples: P<nvc'///V-x, Tlml"- mn. I'ermian. 



II. X.\NMTII>.\. 



A 2)i'<'i*f"i"'l <irintji y iiirliitliiifi x///oo/A, nini-' ,,f less discoidul <nn/ <illio8e keelles* I 

 I'-ftli i>r!initir> gutures. Tli> latter pass through Miim<i-ll<ir><tii x////.- /'// tin i/miim, i>n> 

 subsequently assume fl <i*i>i"<-t <,f Diifwrphoceratidae. /'. ////W lobes retain entire sij> li,t<it 

 saddles tlirniiiilnmt ///"'. ^ t ic<-n>l!^-d fin-Hi^ //"/' i-l,-r,ifi'<l subacute and often keeled venters. 



Family 6. Nannitidae. Anarcestean forms with a tendency to become elevated 

 on the venter in later stages of growth, and having sutures with faintly denticulated 

 lobes and entire saddles, and with very small entire siphonal saddle-. 



Xtuniiffx, rrnxjiliiiiiiift'*, Mojs. (T) Sphaerites, Arthaber. Trias. 



Family 7. Otoceratidae. Involute forms with deep umbilici and prominent 

 ridged umbilical shoulders; venter keeled and acute. Ventral lobes divided by large 

 siphonal saddles. Young have volutions with broad keelleas venter and trapezoidal 

 section. Antisiphonal lobe, so far as known, entire on the sides and bifid at the ends. 



Otoceras, Griesbach ; Anotocerax, gen. nov. Type A. (Prosph.) nala, Diener >p. 

 Triaa 



III. TROPITIDA. 



Includes a large and comparatively homogeneous group of Tri**ic Jails of Anarcestes- 

 liJce aspect, but sutures with peculiarly elongated and completely digitated saddles and lobes. 

 tiiphonal saddles not so deeply incised by marginal lobes as tin Infinity nor very complex 

 i)i outline. Shell* <>rintnti'i>ti-i! ////// costae, often tuberculated, keeled, and chatm* Lit. 

 Aperture invariably u-ifh l"t<rl '/-.>/.>. Connects through Microti-<>jn'fi* n-ith A'c- 



Family 8. Tropitidae. Mojsi>o\-io ( ' r <ir*}. Similar to AHarcestJda* in the 

 ephebic stage, but the young lVe([iiently have volutions with highly trape/oidal 



3. 113.5. 



l;li, Haut-r s]>. 

 Trias ; Sainlli!r_. 

 Ausst'c, Austria. 



Aussee, Austria. 



(Jppei 



sectiona Shells highly ornamented by the intersection of a sy.-tem of longitudinal 

 ridges and transverse costae. Sutures have deep, narrow ventral lobes divided by 

 siphonal saddles with peculiar truncated l>a>e.-, which are often retained in later stages. 

 Sutures in ephebic stages of some form- are -imilar to those of ll<itriti<ln>- : young 

 have a more or less prolonged coronate stage, and are also keeled on the venter an a 

 rule. Aperture narrower and with im-iv pointed ventral crests than in //" /////</,,. 



