560 



MOLLUSCA 



SUB-KINGDOM VI 



denticulated ; and when the saddles are completely divided their marginals are small. 

 Sutures otherwise similar to those of Dinaritidae, and the young have a Dinarites stage. 



Antisiphonal lobe entire and bifid in some forms. 



Buchites, Helictites, Phormedites, Parathisbites, 

 Ghjphidites, Mojs., and perhaps Eudiscoceras, Hyatt. 

 Trias. 



Family 15. Arpaditidae. Differs from UarJu'- 

 tidae in the tendency to form channeled venters 

 bordered by two ridges, Avlrich may be either tuber- 

 culose or smooth. 



Arpadites (Fig. 1146), Klipsteinia, Dittmarites, 

 Muensterites, Steinmannites, Daphnites, Dionites, 

 Drepanites, Heraclites, Guembelites, Cyrtopleurites, and 

 Acanthinites, Mojs. (?) Bosnites, Hauer. Trias. 



Family 16. Trachyceratidae. Discoidal and 

 involute shells with well-defined and often profusely 

 tuberculated costations which are interrupted on the ventral aspect by a smooth zone 

 or channel. This may in some specialised forms become a distinct channel bordered 



Arpadites Cine n si 

 Esino, Lombardy. 



Keuper ; 



Trachyceras Austriacum, Mojs. Upper 

 Trias ; Rothelstein, near Aussee, Austria. 



Protrachyecras An-liehins, Laube. Upper Trias (Xorian) ; 

 Bakony, Hungary (after Mojsisovics). 



by tuberculated ridges. Lobes and saddles completely divided by marginals, but 

 these do not become very long nor complex. 



Distichites, Trachyceras (Fig. 1147), Protrachyceras (Fig. 1148), Anolcites, Sand- 

 lingites, Sirenites, Anasirenites, Diplosirenites, Mojs. Trias. (?) Hesperites, Pompeckj. 

 Rhaetic. 



Family 1 7. Tibetitidae. Compressed involute forms with channeled venter as 

 in Arpaditidae, but sutures generally with adventitious inflections developed through 

 division of the first pair of primitive lateral saddles. Auxiliary series developed by 

 division of the large internal saddles. 



Anatibetites, Tibetites, Paratibetites, Hauerites, Mojs. Trias. 



Family 18. Pinacoceratidae. Mojsisovics. Compressed, more or less involute 

 forms with rounded venter only in primitive species. Sutures greatly complicated, 

 convex, and with adventitious inflections ; also often with a corresponding series of 



