CEPHALOPODA 



G57 



saddles tlian Arietües, and antisiphonal lobe bifid, longer and more coniplex. First 

 pair of doi-sal saddles large and long, otlier 

 dorsal inflections variable, l)ut generally more 

 niinierous tlian in Arietües. 



Schlotheimia Bayle (Fig. 1267); Waeh- 

 neroceras Hyatt. Lower Lias. 



Subfamily D. Polymorphinae Hang. 



Shells compressed discoidal, with smooth 

 young like tliose of Psüoceras. Costae apt 

 to be inclined or slightly signiöidal, and 

 continuous across the venter. Tliis is crenu- 

 lated in primitive forms, biit becomes smooth, 

 Channelled or keeled in specialised shells. 

 The latter have sutures similar to those of 

 Schlotheimia, biit less complex. 



Agassiceras Hyatt {Paroniceras Bonar. ; 

 Gymhites Neumayr ; Amm. glohosum Opp. ; 

 Amm. miserabile Quenst.). Liparoceras Hyatt {Ammonites bechei Sow.) ; Polymorphites 

 Sutner ; Dumortieria Hang ; Amphiceras Gemm. Lias. 



1267. 



Schlotheimia angulata (Schloth.). Lower Lias ; 

 Göppingen, Würteniberg. 



Family 22. Harpoceratidae Neumayr. 



Discoidal and involute shells, with sigmoidal costae. Venter with smooth or crenuloAed 

 keel. Ayerture with curved sides or with projecting lateral ears, and rounded ventral 

 crest. Septa simply digitale, ivith the lobes and saddles arranged in a straight line, and 

 usually with several auxiliary lobes. 



This family, which probably originated from the Arietitinae, ranges from the 

 Lias to the Lower Cretaceous. 



Subfamily A. Harpoce ratin ae Zittel. 

 Discoidal involute shells with sigmoidal costae separated throughout or confluent 



Hildoceras bifrons (Brug.)- Upper Lias ; 

 Whitby, Yorkshire. 



Lioceras opalinnm (Rein.). Lower Dogger ; 

 Teufelsloch, near BoU, Wiirtemberg. 



on the median lateral line, and sometimes bifurcated externally. Nodes never präsent, 

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