314 Annals of the South African Museum. 



Delagoa Bay form than is Kilian's " D. cornuelianum," cited above, to 

 the specimens of the same species figured by Sinzow.* 



Kilian t put " D." martini, var. gottschei, into the group of " D." 

 martini, but if the present specimen is correctly identified with 

 Krenkel's Ammonites, the character of the outer whorl and the 

 suture-line approach the South African form more to the cornuelianum 

 group. The writer, therefore, has raised this variety to an inde- 

 pendent species. There is no differentiation of the peripheral area as 

 there is in the martini group, e. g. in " D." martini, var. orientalis, 

 Jacob. J 



Ch. kiliani, v. Koeneii sp., differs in suture-line, but is close to 

 the South African form as regards costation. The lateral tubercle, 

 however, persists on some of the ribs in v. Koenen's species, and the 

 whorl-section is less depressed. 



The suture-line (only the last one or two are visible, in addition 

 to the immature ones at a diameter of 4 mm.) is characterised by a 

 high external saddle and a very wide lateral saddle. The leaflets 

 subdividing the equally Avide lateral lobe are unusually large, and 

 there is good agreement with the suture-lines of Ch. cornuelianum 

 and Ch. meyendorjfi (d'Orbigny) in Sinzow. || This type of suture- 

 line distinguishes the form here described from the somewhat similar 

 Acantlioplites of the aschiltaensis-bigoureti-bergeroni group ^[ of a higher 

 horizon, but it is interesting to note that in a still later group, namely 

 that of Acanthoceras g/ltairei, Pervinquicre * and A. euomphalus 

 (Sharpe),tt this wide lateral lobe with its prominent, median saddle JJ 



* Ibid., pi. i, figs. 1 and 2. 



t Loc. cit. (1913), p. 340. 



J In Jacob and Tobler, "Gault de la Vallee de FEngelberger Aa," 'Mem. 

 Soc. Pal. Suisse,' vol. xxxiii (1906), pi. i, figs. 1-3. 



Loc. cit. (1902), p. 406, pi. xxxiii, figs. 1 a and b. 



|| Loc. cit., text-figs. 1 and 2, pp. 160 and 164. 



If See Seunes, " Amm. du Gault," 'Bull. Soc. Geol. France' (3), xv (1887), 

 pis. xii-xiv ; and Anthula, " Kreidefoss. d. Kaukasus," ' Beitr. Pal. Ost.-Ung.,' 

 xii (1899), pis. ix-xiii. 



** Cf. loc. cit. (1907), text-fig. 108 on p. 286. 



ft " Foss. Moll. Chalk," ' Mou. Pal. Soc.,' II (1854), p. 31, pi. xiii, figs. 4 a-c. 



JJ See Crick, " Note on A. euomphalus," ' Geol. Mag.,' N.S., dec. iv, vol. vi 

 (1899), pp. 252-3. A specimen of this rare species in the writer's collection 

 has the lateral saddle rather larger than the saddle subdividing the lateral 

 lobe, which, in Crick's figxires, might be mistaken for the former. Sharpe's 

 fig. 4c represents the relative sizes more accvirately. This type of suture-line is 

 a development of that of Acanthoceras cunningtoni, Sharpe sp., and of A. 

 sussexiense, Mantell sp. (Shai-pe, loc. cit., pi. xv, figs. 1 d and 2 c), and the resem- 

 blance to Douvilleiceratidse is a case of convergence. 



