ORDER II AMMONOIDEA 539 
forms becomes divided by an entire azygous lobe on the venter, often termed 
the ‘“siphonal lobe,” but herein after referred to as the ventral lobe, and by 
smaller azygous lobe (shown,to the left in Fig. 1092, 4-C) on the dorsum, 
usually termed the ae 
wntisiphonal. This un- a 
divided ventral lobe eee = oa Oto tha sacs 
(Figs. 1094,1095, EL) eae 
persists throughout © suture-line of Cyrto- Fic. 1094. 
ent 7 clymenia laevigata, Suture-line of Anarcestes subnautilinus, Schloth. 
the Mier ocampylt SO Miinst. Devonian. sp. Devonian. 
far as known, and is 
obliterated by a secondary ventral saddle only in the Gastrocampyli. It is 
present throughout the ontogeny of the sn or radical forms of Hury- 
1s campyli, Glosso- 
So, BS campyli, and 
eee pylt. But 
ieee the Devonian 
al2 all Mesocampyli and 
Fic. 1095. Fic. 1096. Triassic Duzsco- 
Suture-line of Brancoceras sul- Left half of suture-line of Ceratites nodosus, , Pei ies 
catus, Munst. sp. Devonian. de Haan. Trias. 64 mpyli, shells 
having undivided 
ventral lobes have not been recorded ; in the Tirolitidae but one such species has 
been doubtfully described. This class of radicals is replaced in these sub-orders 
by those having the ventral lobe 
divided by a small saddle usually acs . aap yee 
called the ventral or siphonal it pals Z 
saddle (Fig. 1097, m). The class 7 | N38, ~ wp 
of radicals having entire ventral 3 as 2 & oup Be NN 
lobes disappears before the close if 
of the Trias. 
The entire antisiphonal lobe : ; 4: 
has a more extensive distribution EL L ! i LL 
than the entire ventral lobe, being Be eT 
Right suture-line of Coroniceras bisulcatum, Brug. Lias. m, 
present throughout the ontogeny Siphonal saddle; », Line of involution. EL, Ventral (also 
of Microcampyli, Gastrocampyli, and T, First or Gapetlot lntoral tobe? aend oo intenerintaead 
Mesocampyli. Most of the ELury- lobe. ES, LS1, LS2, First, second, and third lateral saddles. 
5 : IS, Dorsal saddle. JL, Antisiphonal lobe. 7, First dorsal lobe 
campyli have this lobe entire, but. lying on line of involution. 
it becomes bifid in the later stages 
of specialised forms. The radicals of Glossocumpyli have it entire, but in 
specialised genera it becomes bifid or even trifid. It is known to be entire 
in only a few of the Lecanitidae, and is bifid in most of the Discocampyli and 
Phyllocampyli, besides having for the most part entire sides. It is also entire 
in some phylogerontic species of the Trias. In the Leptocampyli it is generally 
bifid, but may be trifid or irregular in some species, and is accompanied by an 
extraordinary growth of two of the branches inwards in a large number of 
forms. In Jurassic and Cretaceous Ammonoids, it is as a rule more or less 
lateral lobe and the line of involution are termed auxiliaries, and numbered in regular order. The 
antisiphonal is also known as the internal, dorsal, or columellar lobe. By “lobes” are always 
understood the angulated or digitated portions of the suture which are directed backwards, away 
from the mouth of the shell ; “saddles”’ are the elevations between them, which point towards the 
aperture of the shell.—TRans. | 
