MOLLUSCA 



SUB-KINGDOM VI 



tlie broad inner lateral saddles divided by a pair of shallow lobes into two nearly equal 

 saddles. Ventral lobe in primitive Dimeroceras undivided, and this together with the 

 sutures indicates common ancestry with Brancoceras and Magnosellandae. Aperture 

 with broad shallow hyponomic sinus. Shells have annular costae crossing the venter. 



Dimeroceras, Hyatt ; Pericydus, Mojs. Devonian and Carboniferous. 



Family 3. Grlyphioceratidae. Ammoniticones of variable form, including dis- 

 coidal and highly involute shells, and also a large proportion of Anarcestes-like genera. 

 Septa concave along the mesal 

 plane in primitive Branco- 

 ceras, but becoming convex 

 as a rule along this plane in 

 the later stages of other 

 genera. Ventral lobe entire 

 in primitive forms, but be- 

 coming divided in more 

 specialised genera. External 

 sutures similar to those of 

 Magnosellaridae, but dorsal 

 sutures have narrow saddles 

 011 either side of the entire 

 pointed antisiphonal lobe. 



FIG. 1130. 



Suture -line of Brancoceras 

 sulcat-us, Miinst. sp. Upper 

 Devonian ; Fichtelgebirge. 



Brancoceras rotatorius, 

 Tournay, Belgium. 



Fi<;. 1131. 

 de Kon. sp. 



Carboniferous Limestone ; 



Siphuncle small, and funnels generally diplochoanitic, except in species with undivided 



ventral lobes. Aper- 

 ture usually with 

 hyponomic sinus, but 

 some species have 

 ventral crests during 

 ephebic stages. Shells 

 smooth, tuberculated 

 or costated, but c< >si ne 

 do not cross the. 

 venter as a rule. 

 Venter sometimes 

 with well - marked 

 Gly&wceras*ri'"('>-";>>*, <;,,idf. i oll gitudinal ridges. 



sp. Carboniferous Limestone ; '?. 



Suttrop, Westphalia. Brancoceras ( igs. 



1130, 1131); Muen- 



1134), Parti li'iini-c rn. ^ 



FK;. I 1 :;:.'. 



<;<t*trioceras Jossae, M. V. K. Permo-Carbon- 

 iferous ; Artinsk, Ural. 



steroceras, Gastrioceras (Fig. 1132), Gtyphioceras (Figs. 1133, 

 Schistoceras, Hyatt ; Pronannites, Haug. Devonian and 

 Carboniferous. 



Family 4. Dimorphoceratidae. Discoidal compressed 

 shells ; primitive species like Prolecanites, but specialised forms 

 are more or less involute, although still retaining modified 

 Anarcestean aspect. Lobes become digitated, beginning with 

 the arms of the ventral lobe and progressing inwards, but 

 bases of saddles remain entire. The broad undivided saddles of Macjnosellaridae are 



Fid. 1134. 



(iti/iihifH'i'rti.x <i:<i<lri,t, Gohlf. 

 sp. Carboniferous Limestone ; 

 Choquier, near Liege, Belgium. 



