CEPHALOPODA 



631 



two broad saddles on either side, but more specialised sliells may have two pairs of 

 principal saddles fornied by division of the primitive first laterals. There is a corre- 

 sponding development of narrow saddles and lobes on the dorsum, but primitive forma 

 liave only two broad saddles here as in Änarcestes. Antisiplional lobe narrow, entire, 

 pointed. From this family sprang tbe Glyphioceratidae of the Carboniferous, and 

 through them came the Tropitidae and Arcestidae of the Triassic. 



Gheiloceras Frech {Parodoceras Hyatt); Sporadoceras (Fig. 1175); Aganides Montfort 

 (Figs. 1177, 1178). Devonian and Carboniferous. 



Family 6. Gephyroceratidae Hang. 



Evolute to involute forms^ mostly laterally compressed, with short body-chamhers^ deep 

 ventral hyponomic sinus, and without labial constric- a 



tions. This group includes forms with simple 

 goniatitic septa, forms with ceratitic septa, and forms 

 with exceedingly complex ammonitic septa. 



The external sutures in primitive forms some- 

 times approximate to those of Änarcestes, but the 

 dorsals have only one large azygous lobe, the saddle 

 being confluent at the line of Involution with the 

 second external pair. In more involute forms the 

 antisiphonal lobe is large, entire and pointed ; there 

 is one pair of dorsal saddles, and one of broad 

 dorsal lobes ; the second pair of saddles, when 

 present, is confluent with the second pair of lateral 

 saddles, 



Subfamily A. Primordialinae Hyatt 

 (Primordiales Beyrich). 



Distinguished from Änarcestes by the divided 

 ventral lobes, large siphonal saddles, and especially 

 the first lateral saddles, which are very prominent 

 on the sides. Adventitious lobes and saddles are />„^fc„.„.,.„.,,„/„™<,„..^,/R„„, % TTr^r^or 



Gephyroceras intumescens(iiejT.). Upper 



formed by division of the first lateral saddles. Septa Devonian ; Nassau. A, Conch, i/i- -B. 

 in the young are concave and similar to those of " ^^^' '°^" 



Änarcestes, but in later stages become convex along the mesal plane as in typical 

 Ammonoids. Siphuncle small, subventran, without calcareous sheath ; funnels retro- 

 siphonate and short, except in Manticoceras, where they are prosiphonate. 



Gephyroceras (Figs. 1138, 1179), ikTavifzcoceras Hyatt; iVo6e/oceras Clarke ; Timanites 

 Mojs. Devonian. Nomismoceras Hyatt. Gonioloboceras Hyatt. Type G. (Goniatites) 

 goniolobus (Meek). Carboniferous. • Koenenites Wedekind. Devonian. (This and 

 related genera are described by Wedekind in Sitzher. Ges. Naturf. Freunde Berlin, 1913). 



From the Gephyroceratidae probably sprang the Meekoceratidae of the Permian 

 and the Lower Trias, and through them came the Ceratitidae. 



Fio. 1179. 



Subfamily B. Beloceratinae Fi-ech. 



Form compressed, discoidal, involute, with high whorls and narrow acute venters. 

 Lobes and saddles lanceolate, with numerous adventitious and auxiliary lobes. 



Includes the genus Beloceras Hyatt (Fig. 1 1 80), of the Upper Devonian. From 

 the Beloceratinae probably came the Sageceratinae, the Hedenstroeminae, and the 

 Carnitinae, and possibly the Pinacoceratidae. Beloceras was probably derived from 

 Timanites with Probeloceras as a connecting link. 



