AEGOCERAS CHARMASSEI. 323 



The lobe-line is very complicated, the symmetrical septa being divided into five 

 lobes and saddles, all formed of unequal parts. The siphonal lobe is small, and 

 terminates in three short branches, two of which are bifid ; the siphonal saddle is much 

 wider than the principal lateral lobe, and forms an arch with three terminal festoons. 

 The principal lateral lobe is large, and has a branched termination in three irregular 

 digits and three small lateral prolongations on each side ; the lateral saddle is as wide 

 as the principal lateral lobe, and ends in three irregular-shaped festoons ; the lower 

 lateral lobe is narrow and oblique, and ends in three digits ; the three auxiliary lobes are 

 placed very oblique, they diminish in size as they approach the umbilicus, and end in a 

 small trifid digit (PI. XVII, fig. 1). 



Affinities and Differences. — This Ammonite very much resembles Aegoeeras angulatum, 

 but the smoothness of the sides of the whorls, in consequence of the absence of ribs and 

 the development of the short, oblique, crenulated series around the outer margin, with its 

 smooth centre in the siphonal area, and a difference in the dimensions of the lobe-line, 

 induced d'Orbigny to separate it under the name Moreanus. I am inclined to consider 

 it only a variety of angulatum and not a distinct species. This Ammonite characterises 

 a particular horizon of life very rich in fossils in the Cote-d'Or. 



Locality and StratigrapMcal Position. — This species is found in a dark grey shale 

 near Charmouth, from whence all my specimens have been obtained. Young forms of 

 Gryphaea arcuata make their appearance for the first time in this bed; one of these 

 Oysters has become firmly adherent to the shell I have figured. 



Professor d'Orbigny says it characterises the inferior beds of the Lower Lias, 

 which lie below the Gryphcea arcuata; the figured specimen was collected at Pont- 

 Aubert near Avallon, Yonne, where it is very rare. M. Martin says this Ammonite 

 distinguishes the zone of Ammonites Moreanus in the Department of the Cote-d'Or, and 

 the reader is referred to his classical work on the Infra-Lias of that Department for an 

 admirable account of the rich fauna it contains. 



Aegoceras Charmassei, d'Orbigny. PI. XX, figs. 1 — 3. 



Ammonites sulcatus, Simpson? Monogr. of Ammonites, York. Lias, p. 55, 1843. 



— Charmassei, d'Orbigny. Paleontol. Eranc., Terr. Jurass., i, p. 296, 



pis. xci, xcii, 1844. 



— sulcatus, Buchnan. Murchison's Geology of Cheltenham, 2nd ed., 



p. 91, pi. ii, figs. 1—3, 1845. 



— angulatus, Quenstedt. Die Cephalopoden, p. 262, 1847. 



— Charmassei, Kudernatsch. Jahrbuch der k. k. geologischen Reichsaustalt 



iiHeft, p. 173, 1851. 



— — Savi e Meneghini. Considerazioni sulla Gleologia dellaTos- 



cana, p. 104, 1851. 



— — Meneghini. Nuovi fossili Toscani, p. 12, 1853. 



