CLASS V 



CEPHALOPODA 



657 



saddles than Arietites, and antisiphonal lobe bifid, longer and more complex. First 

 pair of dorsal saddles large and long, otlier 

 dorsal inflections variable, Imt generally more 

 numerous than in Arietites. 



Schlotheimia Bayle (Fig. 1267); Waeh- 

 neroceras Hyatt. Lower Lias. 



Subfamily D. Polymorphinae Haug. 



Shells compressed discoidal, with smooth 

 young like those of Psiloceras. Costae apt 

 to be inclined or slightly sigmoidal, and 

 continuous across the venter. This is crenu- 

 lated in primitive forms, but becomes smooth, 

 cliannelled or keeled in specialised shells. 

 The latter have sutures similar to those of 

 Schlotheimia, but less complex. 



Agassiceras Hyatt {Paroniceras Bonar. ; 

 Gymbites Neumayr ; Amm. glohosum 0\)\). ; 

 Amin. miserabile Quenst.). Liparoceras Hyatt (Ammonites bechei Sow.) ; Pohjmorphites 

 Sutner ; Dumortieria Haug ; Amphiceras Gemm. Lias. 



Family 22. Harpoceratidae Neumayr. 



Discoidal and involute shells, with sigmoidal costae. Vender icith smooth or crenulated 

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

 crest. Septa simply digitate, loith the lobes and saddles arranged in a straight line, and 

 usually with several auxiliary lobes. 



This family, which i)robably originated from the Arietitinae, ranges from the 

 Lias to the Lower Cretaceous. 



Vu:. 1267. 



Srhhthtimia anijulatu (Schlotli.). Lower Lias ; 

 Goppingen, Wiirteniberg. 



Subfamily A. Harpoceratinae Zittel. 

 Discoidal involute shells with sigmoidal costae separated throughout or confluent 



Fig. 12(58. 



Hildoccras bifrons (Brug.). Upper Lias ; 

 Whitby, Yorkshire. 



Fig. 1269. 



Lioceras opnlinum (Rein.). Lower Dogger ; 

 Teiifelsloch, near Boll, Wiirtemberg. 



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

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