78 POMPECKJ. JURASSIC FAUNA OF CAPE FLORA. [NORW. POL. EXP. 



external side with coarser, less curved ribs. The advanced stage of this 

 form has been illustrated by d'Orbigny 1 as Amm. modiolaris. In the 

 above-mentioned publications of the English Geological Survey, this form 

 has been delineated as Amm. modiolaris Luid. The full-grown speci- 

 mens of this species differ from those of Cadoceras sublceve Sow. sp. 

 in having a wider umbilicus, and the whorls being in transverse direc- 

 tion less closely encircling, and hence lower (with a coarser sculpturing 

 in the medium stages of growth). This second species of the English 

 Jura I designate Amm. (Cadoceras) modiolaris d'Orb. 



3. Nikitin 2 reports that be has observed Cadoceras Tchefkini d'Orb. sp. 

 from the English Kellaways Rock in English museums. 



4. Yet another form of Cadocerates from the Wiltshire Kellaways Rock - 

 n. sp. indet. is before me. Up to a diameter of 60 mm. it is charac- 

 terised by remarkably flat whorls, with a narrow umbilicus and close-set 

 fine ribs with a decided flexure forwards. From its outward shape, it 

 should be placed between Cad. sublceve Sow. sp. and Cad. stenolobum 

 (Keys.) Nik. 



The two first-named species are the Western European representatives 

 of two large groups of Cadocerates, which, especially in the Russian Callovien 

 attain a particularly high degree of development, 



Upon Cadoceras sublceve Sow. sp. follow all those forms which are cha- 

 racterised in their earlier stages by a narrow umbilicus and high-mouthed 

 whorls with fine falciform ribs. Even in advanced stages these forms gener- 

 ally have a narrow umbilicus, e. g. : 

 Cadoceras n. sp. indet. (No. 4 on p. 72). 



n. sp. indet., a similar form from the "Ornatenthon" of Suabia. 



Seebachi Behr. (Amm. sublaevis v. Seeb.) 3 



placenta (Bean, m-s.) Leek. sp. 



Tchefkini d'Orb. sp. 



Wosnessenski Grew. 



stenolobum (Keys.) Nik. 



Nanseni n. sp. (see below) 



1 A. d'Orbigny, 'Paleontologie franchise'. Terr. jur. I. p. 468, pi. 170. 



2 Bulletin de la Soc. Belg. de Geologic etc. vol. III. p. 34. 



8 Different allied forms, yet undescribed, occur in the "Ornatenthon" of north western 

 Germany, as 1 have seen in the Gottingen Museum. 



