bo 
be MOLLUSCA SUB-KINGDOM VI 
the 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 Magnosellaridae. Aperture 
with broad shallow hyponomic sinus. Shells have annular costae crossing the venter. 
Dimeroceras, Hyatt ; Pericyclus, Mojs. Devonian and Carboniferous. 
Family 3. Glyphioceratidae. 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 
speciahsed genera. External 
sutures similar to those of 
Magnosellaridae, but dorsal 
sutures have narrow saddles 
on either side of the entire 
pointed antisiphonal _ lobe. 

Fic. 1130. 
Suture-line of Brancoceras Be ee 
sulcatus, Miinst. sp. Upper Brancoceras votutorius, de Kon. sp. Carboniferous Limestone ; 
Devonian ; Fichtelgebirge. Tournay, Belgium. 
Siphuncle small, and funnels generally diplochoanitic, except in species with undivided 
ventral lobes. Aper- 
ture usually with 
hyponomie sinus, but 
some species have 
ventral crests during 
ephebiestages. Shells 
smooth, tubereulated 
or costated, but costae 
do not cross the 
venter as a rule. 
Venter ‘sometimes 

Fic, 1133. with well - marked 
Glyphioceras sphaericus, Golaf. oO} j idoes 
__Gastrioceras Jossae, M. V. K. Permo-Carbon- sp. Carboniferous Limestone ; longitudinal ridges. 
iferous ; Artinsk, Ural. Suttrop, Westphalia. Brancoceras (Figs. 
1130, 1131) ; Muen- 
steroceras, Gustrioceras (Fig. 1132), Glyphioceras (Figs. 11338, 1134), Paralegoceras, 
Schistoceras, Hyatt; Pronannites, Haug. Devonian and 
~ Carboniferous. = df or 
Family 4. Dimorphoceratidae. Discoidal compressed V | 
shells ; primitive species like Prolecanites, but specialised forms Ria. 1184. 
are more or less involute, although still retaining modified Glyphioceras diadema, Goldf. 
Anarcestean aspect. Lobes become digitated, beginning with sp. Carboniferous Limestone ; 
= P os Choquier, near Liége, Belgium. 
the arms of the ventral lobe and progressing inwards, but 
bases of saddles remain entire. The broad undivided saddles of Magnosellaridae are 
