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, 
Glyphidites, Mojs., and perhaps ELudiscoceras, Hyatt. 
Trias. 
Family 15. Arpaditidae. Differs from Buchi- 
tidae in the tendency to form channeled venters 
bordered by two ridges, which may be either tuber- 
culose or smooth. 
Arpadites (Fig. 1146), Klipsteinia, Dittmarites, 
Muensterites, Steinmannites, Daphnites, Dionites, 
Drepanites, Heraclites, Guembelites, Cyrtoplewrites, and 
Fic. 1146. Acanthinites, Mojs. (?) Bosnites, Hauer. Trias. 
ane etapa eee SHER SERGE 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 


Fic. 1147. Fic. 1148. 
Trachyceras Austriacum, Mojs. Upper Protrachyceras Archelaus, Laube. Upper Trias (Norian); 
Trias; Rothelstein, near Aussee, Austria. 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, Pompeck). 
Rhaetic. 
Family 17.’ 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 
