OUDKK II 



AMMONOIDKA 



539 



Pro. 



Suturr-linr of Cyrto- 

 <///; /i i' laevigata, 



Munst. 



L /;/, 



FlO. HI!'!. 



*u\m-,' \\i'<>tAnarce8tessubnaittiHnus, Schlotli. 

 I- \onian. 



forms becomes divided by an entire azygous lobe on the \mt.-r, often 

 the "siphonal lobe," but herein after referred to as the //////>////*, and by 

 a smaller azygous lobe (shown to "the left in Fig. 1092, A-C) on the dorsum, 

 usually termed the 

 antisiphonal. This un- 

 divided ventral lobe 

 (Figs. 1094, 1095, EL) 

 persists throughout 

 the Microcampyli so 

 far as known, and is 

 obliterated by a secondary ventral saddle only in the Gastrocampyli. It is 

 present throughout the ontogeny of the simplest or radical forms of Eury- 



campyli, Glosso- 

 campyli, and 

 Phyllocampyli. But 

 in the Devonian 

 L ! ' :I - "'- <' 11 l L EL Mesocampyli and 



FIG. 1095. FIG. 1096. Triassic Disco- 



Suture-line of Brancoceras sul- Left half of suture-line of Ceratites nodosus, . n ..i a V.11a 



<-t,i*, Miinst. sp. Devonian. de Haan. Trias. ^ampyil, 



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 

 called the ventral or siphonal 

 saddle (Fig. 1097, m). The class 

 of radicals having entire ventral 

 lobes disappears before the close 

 of the Trias. 



The entire antisiphonal lobe 

 has a more extensive distribution 

 than the entire ventral lobe, being 



Bight Bature-liH6 of Coroniceras bisttiaatum, Bru^, 



, . Lias, m, 



EL. V.-ntral (also 



* u, ; . ,,,,,,,,*. 



ES, /..s 1 ', /.N-, First, second, and third lateral sa-1- ll.-s. 



. .1 i 4.1, 



present throughout the Ontogeny ^i lt \ ltniA l sa.i.ll.-; , Line of involution. 



of Microcampyli, Gastrocampyli, and jBg 



Most Of the Ev/ni- lobe. 



*.v ! T. i.- u \ IS > D sae. ,, n 



have thlS lobe entire, but lying on line of involution. 



it becomes bifid in the later stages 



of specialised forms. The radicals of Glossocampyli 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 Leptocampi/li 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 columdlar 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.] 



