AMMONITES. — ZOOLOGICAL, ETC. 



323 



1st. division. Groups which are not found in the Creta- 

 ceous formation, but are peculiar to the Jurassic. 



Arietes, Buch, peculiar to the lower lias. 



Falciferi, Buch, peculiar to the upper lias, 



Amalthei, Buch, peculiar to the different beds of the 

 Jurassic formation, 



Ornati, Buch, peculiar to the Oxford clay. 



Capricorni, Buch, from the Jurassic, or Oolitic formation. 



Coronarii, Buch, peculiar to the lower oolite. 



Armatif Buch, peculiar to the upper strata of the Jurassic 

 formation. 



2nd division. Groups containing species, peculiar both to 

 the oolitic, or Jurassic and cretaceous formations. 



Heferophylli, d'Orbigny, peculiar to the upper lias in the 

 Jurassic formation, are only found in the cretaceous forma- 

 tion, in the lower Neocomien and gault. The species, al- 

 though found in the two formations, are nevertheless clearly 

 distinguished from each other ; the species from the Jurassic 

 formation, having their saddles formed of unequal parts, 

 and those of the Cretaceous formation of equal parts. 



Macrocephali, Buch, are peculiar to the Jurassic formation, 

 and are also found, but in very small numbers, in the lowest 

 cretaceous strata, (lower Neocomien), the nearest the epoch at 

 which the principal portion of the group lived. 



Fimbriati, d'Orb., of which hardly two species exist in the 

 lower Jurassic formation, whilst there are, in the Neocomien 

 alone, twelve species which do not extend to the upper por- 

 tion of the cretaceous formation. 



Planulati, Buch, this group, which is peculiar to the Ju- 

 rassic formation, has furnished me with three species in the 

 Neocomien. 



3rd division. Groups peculiar to the Cretaceous formations, 

 Cristati, d'Orb., these are found in small number in the 

 Neocomien, are at their maximum in the gault, and are re- 



VOL. I.— NO. X, Z 



