NO- ^•] DESCRIPTION OF THE FOSSILS. 



83 



PI. II. fig. 7 b: a, 61, 62, a, hi, a, 61, 61, U, a, a, bi, Ua, 62, a, 62. (17 ribs 

 on the umbilicus - 7 entire ribs, 10 bifurcated ribs -, 27 ribs on tbe out- 

 side). At about 30 mm. in diameter, the sickle form disappears. The nbs, 

 almost straight, run across the flanks in a flat curve; near the external side, 

 however, they continue to be much bent forward. At this size the ribs on 

 the wall of the umbilicus begin to become less distinct, no longer radiating 

 from the umbilicus-seam, but beginning somewhat higher. 



At 9 mm. of the height of the whorl (about 18 mm. in diameter), the 



somewhat asymmetrical lobe-line exhibits the development represented in the 



_ letterpress fig. 15 a. The narrowing at the base of the 



•flf '%f\F'^^, second lateral saddle and of the first auxiliary saddle is 



worthy of notice. The narrowing becomes still greater, 



^^!iemni%TZ ^' *^ g™^th proceeds, as letterpress fig. 15 b shows, 



figS^tlShfight of' corresponding to the lobe-line of the size with a diame- 



^''Xenla^rg^ed!™' *^'' °^ ^^ "''"• ^^^ lobe-line - letterpress fig. 15 a b 



differs from the drawing, which Count Keyserling gives 



of a young specimen in the greater narrowness of the 



saddles 1. On the other hand, the letterpress figure 



b) Lobe-line of PI. II. 15 b agrees very well with the lobe-fine of a specimen 



fig- 7 a, from the 2nd .... . . t, 



lateral lobe, at a height 01 Similar Size from the Russian Jura (from Rybinsk), 



of the whorl of 16 mm. rpi r 1. iu 1 ii_ -i- in 1 



2 X enlarged. ^"^ l^^t that the auxiliary saddles are narrowed to a 



considerable degree in the present specimens from Cape 

 Flora, is owing to the asymmetry of the lobe-fine. The drawing — letter- 

 press fig. 15 a — is taken from the side of the suture, somewhat short- 

 ened on account of the asymmetry of the lobe-fine; the other side could 

 not be observed ^. 



Of larger specimens of Cadoceras Tchefkini, there are only two fragments 

 of smooth body-chambers among the material collected by Prof. Nansen at 

 Cape Flora. The larger of the two agrees well in its transversely great 



' Krusenstern and Keyserling: 1. c. pi. XXII. fig. 11. 



^ The second lateral saddle only widens with the commencement of the increased 

 widening of the whorls, and then it shows the form so well figured by Count 

 Keyserling — 1, c. pi. XXII. fig. 12. In larger specimens the edge of the umbilicus 

 passes through the second lateral saddle. Even in large specimens the auxiliary 

 saddles remain narrow. 



