90 POMPEGKJ. JURASSIC FAUNA OF CAPE FLORA, [norw. POL. EXP. 



macrocepMlxm Nikitin^ is incorrect; the umbilicus there is much narrower, 

 the ribs have a more radial direction, and single ribs seem to be altogether 

 absent (1. c. fig. 44 b). 



If Newton's figures do not agree with Macrocephalites macrocephalus. 

 Scbloth. sp., they agree perfectly in form and sculpture with Cadoceras Nan- 

 seni n. sp. here described. This is especially the case with regard to New- 

 ton's fig. 1 ; but PL XXXIX. fig. 2 in Newton, might also be identified, from 

 the sculpturing, with our species. The umbilicus in fig. 2 is most probably in- 

 correctly drawn, as also the centre of the umbilicus in fig. 1 (1. c. PI. XXXIX. 

 fig. 3 with more inflated whorls, Newton only refers, with reservations, to 

 Amm. macrocephalus. From the sculpture and the width of the umbilicus, 

 neither can this specimen be referred to Macrocephalites macrocephalus 

 Scbloth. sp. It is a Cadoceras bearing a strong resemblance in its sculptur- 

 ing to Cadoceras Nanseni n. sp., but which, on account of the thicker 

 whorls should rather be regarded as separate [Cadoceras sp. indet. PI. II. 

 fig. 8].) 



Amm. {Cadoceras) Tchefkini (d'Orb.) E. T. Newton e. p. — 1. c. PI. 

 XXXIX. fig. 6 — cannot be referred to Cadoceras Tchefkini d'Orb. sp., on 

 account of the wider umbilicus, the lower whorls, and the less pronounced 

 involution, but must be associated with Cadoceras Nanseni n. sp. 



The fact that the full-grown stage of Cadoceras Nanseni, which Newton 

 determined as Amm. {Cadoceras) modiolaris Luid. — 1. c. PI. XXXIX. fig. 10, 

 differs from those species of Cadoceras modiolaris Luid. of English Authors, 

 was expressed by Newton in the words "flattened variety", "more com- 

 pressed", etc. 



Remarks. Judging from its form and sculpturing, and the lobe-line of 

 the young whorls, Cadoceras Nanseni n. sp. is very closely allied to Cado- 

 ceras Tchefkini d'Orb. sp. As regards the young whorls, the new species dif- 

 fers from Cadoceras Tchefkini: (1st) in the greater width of the umbilicus — 

 compare letter-press fig. 16 a and PI. II. fig. 7 — ; (2nd) in the somewhat 



" S. Nikitin, 'Der Jura der Umgegend von Elatma'. Lfg. 2. PI. VIII. fig. 44. 



