SUPPLEMENT 



TO 



A MONOGRAPH 



OF THE 



MOLLUSCA FROM THE GREAT OOLITE. 



CEPHALOPODA. 



Ammonites Bullatus, D'Orhi(/. Tab. XXXI, fig. 1. 



Ammonites Bullatus, D'Orb. Pal. Fr. Ter. Jiirass., p. 412, pi. 142, figs. 1 and 2. 



— — Kiidernatsch. Abliand. K. K. Geo). Reich., 1 band., taf. iii, 



figs. 1—4—11. 



— PLATYSTOMUs, Quenst.1 Cephal., t. 1.5, fig. 3. 

 ■ — Bullatus, Oppel. Juraform., p. 519. 



— — Quenstedt.1 Der Jura., t. G4, fig. 13, p. 4/9. 



Testct hullatd, Irregulari ; mifraciibiis subinvoluiis, latis, ultimo (mgustato, transversim 

 late costato ; costi.s iiiaqualibus ; apertiirci constrictd, semilunari. (D'Orbigny.) 



Shell inflated, globose, variable in form tbroughont all the stages of its growth, orna- 

 mented with large, transverse, slightly elevated ribs, which pass from the umbilicus over 

 the back to the other side, not straight, but curved forwards ; these are separated by other 

 shorter ribs, which alternate with the larger series of ribs in the adult state, but in the 

 young state there are two and sometimes three short ribs between each of the longer 

 ones. The volutions of the spire are irregular and embracing, forming a contracted um- 

 bilicus in the young state ; subsequently the volutions are less contracted, which renders 

 the shell unsymmetrical or deformed. The back is rounded, the mouth much contracted 

 and prolonged in the middle part. The septa are very much complicated. 



In England this Ammonite is veiy rare. The aged example figured is seven inches in 



