558 



MOLLUSCA 



SUB-KINGDOM VI 



Family 9. Celtitidae. Primitive forms discoidal, compressed, and costated. 

 The costae in some cross the venter, and are also developed after a tuberculated stage 

 as in Sibiritidae. Sutures in these are often entire, the ventral lobe undivided (Oyclo- 

 celtites), and there may be but one pair of principal laterals, or at most two pairs, 

 with one pair of auxiliary lobes. Affinity with Ibergiceras and Lecanitidae is indicated 

 by the sutures of these shells. Specialised forms have smooth zones or keels on the 

 venter. Antisiphonal lobe entire in primitive genera, becoming bifid in specialised 

 forms and often very long. Costae and all characters, except sutures in some genera 

 (Arniotites) approximate closely to Liassic forms. 



Cycloceltites, Geltites, Styrites, Tropiceltites, Arnioceltites, and perhaps Haidingerites, 



FIG. 1143. 



Ceratites nodosus, de Haan. Muschelkalk ; Wurzburg, Bavaria. A, B, Conch, 1/3- C, Left half of suture- 

 line. D, First and second lateral saddles and auxiliaries to left of line of involution (?i) ; half of dorsal suture- 

 line to right. (AL, Antisiphonal lobe ; other lettering as in Figs. 1096-1097.) 



Mojs. ; Arniotites, Hyatt ; Florianites, gen. nov. Type F, (Gelt.) Floriani, Mojs. sp. 

 Trias. 



Family 10. Sibiritidae. Mojsisovics. Primitive forms discoidal and often 

 tuberculated, giving rise to involute and compressed shells, without tubercles and with 

 slighter costae. The costae usually cross the venter and are often more or less con- 

 vergent to nodes on the ventro -lateral angles of some shells, which usually have a broad 

 venter and more or less trapezoidal section. The nodes disappear in later stages, when 

 the sides generally become more rounded, and the venter more elevated. Sutures have 

 divided ventral lobes, with divided siphonal saddles. Lateral inflections entire in 

 primitive, but in specialised forms the lobes become denticulated. 



Stephanites, Waagen; Sibirites, Anasibirites, Metasibirites, I'hetidites, Mojs.; Para- 

 stephanites, gen. nov. Type P. (Achroch.*) atavus, Waagen sp. Pseudoceltites, gen. nov. 

 Type P. (Celt.) multiplicatut, Waagen sp. Trias. 



Family 11. Ceratitidae. Mojsisovics (pars). Primitive forms discoidal or 



