NO. 2.] DESCRIPTION OF THE FOSSILS 99 



I wish to point out that the form from the Russian Jura, which d'Orbigny 

 at first ^ determined as Amm. LeacM subsequently ^ as Amm. Maries is 

 aUied to our Quenstedtoceras vertumnuni, but differs from it in its finer 

 sculpturing, — without single ribs, — and in its lower saddles (provided 

 d'Orbigny's drawing is correct). Nikitin^ refers the form in question to the 

 synonyms of Quenstedtoceras Lamberti Sow. sp. It is probable that both 

 d'Orbigny's and Nikitin's determinations are wrong, and that this Amm. Leachi 

 d'Orb. non Sow. = Amm. Marice d'Orb. e. p. = Quenstedtoceras Lamberti 

 (Sow.) Nik. e. p., belongs to the group of Quenstedtoceras Mologoe-Ryb- 

 inskianum. 



Quenstedtoceras vertumnum Sintzow and Mologce Nik. are the Quenstedto- 

 ceras in which one of the generic characters — the formation of the keel- 

 line — is quite suppressed, or perhaps only nearly so, i. e. with the exception 

 of the whorls of still younger stages than those hitherto studied. These 

 forms have consequently still more resemblance to the Cadocerales than all 

 other species of Quenstedtoceras, which in adult stages also become broad and 

 depressed. 



In the material collected by Professor Nansen in the neighbourhood of 

 Cape Flora, the following forms of Ammonites may be recognized after the 

 above investigations: 



Macrocephalites Kcettlitzi n. sp. 



„ sp. 



Cadoceras Tchefkini d'Orb. sp. 

 „ Nanseni n. sp. 

 „ sp. ex. aff. Nanseni (n. sp.) 

 „ Frearsi (d'Orb. sp.) Nik. 



sp. (?ElatmcB Nik.) 

 „ sp. indet. 

 Quenstedtoceras vertumnum Sintz. 



' Murchison, Verneuil et Keyserling, 'Geologic de la Russie' Vol. U. Paleonlologie, p. 

 438, PI. XXXV. fig. 7-9. 



2 'Paleontologie frangaise' Terr. jur. I, PL 179. fig. 7-9. 



3 S. Nikitin, 1881. Rybinsk etc. p. 4«, 



