CLASS V CEPHALOPODA 603 



Hercofjlossa Conrad {Enclimatoceras Hyatt) (Fig. 111'7). Deeply involute, with 

 sutures like those in Glyphioceratidae, Ijut the ventral saddle not divided by even the 

 shallow lobe nsually found in tliat faniily. Annular lobes present 

 only in some species. Siplumcle small, centren or dorsad of centre. 

 Trias to Tertiary. 



Pseudonautüus Meek. Similar to Hercoglossa, but with lobes 

 on the venter, and two saddles on either side. Large annular 

 lobes present. Jura. 



Äturia, Bronn (Fig. 1118). Similar to Hercoglossa, but with 

 large siphuncle close to the dorsuni from an early stage onward, 

 and funnels very long and larger than in any genus of Mesozoic 

 or Tertiary Nautiloids. Eocene and Miocene. 



IV. Ryticeratida Hyatt. 

 Cyrtoceracones, gyroceracones and naütüicones having shells ^^^'" ■'^^.^" 



covered with more or less projecting hands of groivth which often Mioce^ef Bordeaux'. 



hecome sinuous or develop into spout-like spinöse, or nodose pronii- ^^^^'^ broken open to 



r .1 ' T 1 1 n .1 , , 7 /. , Show siphonal funnels. 



nences. In the more speciahsed shells these are apt to he confined 



to the venter. The frills in the hands often form coarse longitudinal ridges. Siphuncle 

 tubulär or slightly nummuloidal, and commonly ventrad of centre. 



Family 11. Halloceratidae Hyatt. 



Orthoceracones and cyrfoceracones having depressed elliptical or suh-trigonal sections, 

 venter hroader than the dorsum, Shell with closely set and frilled projecting hands of 

 growth, having large ring-like hands at intervals that sometimes expand so as to form 

 wide collars. The highly specialised nautilicones may have a row of large nodes on 

 either side springing from the hases of large spout-like spines. Siphuncle tubulär ^ small, 

 and near the venter. 



Zitteloceras Hyatt. Cyrtoceracones of depressed elliptical section, the venter 

 narrower and more gibbous than the dorsum. The layers finely frilled and closely 

 set in the intervals between more prominent annular bands. Ordovician to Devonian. 



Halloceras Hyatt. Gyroceracones of sub-trigonal section, the venter broad and 

 dorsum sub-angular, with one row of large nodes at each of the ventro-lateral angles. 

 Devonian. 



Family 12. Ryticeratidae Hyatt. 



Cyrtoceracones and gyroceracones resemhling Halloceratidae, but much larger, with 

 coarser crenulated bands, and often with rows of spout-like spinous processes which some- 

 times form coarse longitudinal ridges. Siphuncle more or less nummuloidal, and larger 

 than in the Halloceratidae. 



Ryticeras Hyatt {Rutoceras Hyatt), Cophinoceras, Strophiceras Hyatt. Devonian. 



V. Khadinoceratida Hyatt. 



Cyrtoceracones, gyroceracones and nautilicones having smooth or spinous longitudinal 

 ridges in the young, which hecome large and ßuted in some genera, hut disappear in 

 others. Ridges more or less sporadically comhined with fold-like annulations, thus 

 suggesting direct descent from the Kionoceratidae. 



Family 13. Rhadinoceratidae Hyatt. 



Primitive discoidal gyroceracones and nautilicones ivith stout volutions, circular or 

 depressed elliptical in section, but hecoming reniform in later stages of nautilicones. 



