On Cretaceous Cephalopoda from Zululand. 233 



Morton sp., is considerably closer to the present species, as is one of 

 the specimens figured by Whitfield,* which latter example, however, is 

 of a considerably larger size. These forms of the delatvarense-group, 

 however, neither have the overhanging umbilical edge, nor the close 

 costation of the present species, though they are nearer to the latter 

 than is any other of the very numerous species of Mortoniceras 

 described. 



Perviuquicref doubtfully recorded M. delawarense (with varieties) 

 from Tunis, but his specimens are much more strongly tuberculate 

 than the new form here described and thus resemble M. campaniense, 

 Grossouvre, which species subsequently was united by its author 

 with 3/. delawarense. 



One characteristic feature of these forms of the delawarense group 

 is the weakening of the wide and low keel, carried to extremes in the 

 fragment figured as M. delawarense by Julia A. Gardner.* It is 

 difficult, from an inspection of the figure, to form an opinion as to the 

 exact relationship of this form, for it has an almost flat, Hoplites-like 

 ventral area. At any rate, its convergence towards such a form as the 

 Upper Campanian A. marroti (Coquaud), Grossouvre, is striking. 



None of the species of Mortoniceras from the European Senoniau 

 resemble the form here described. The suture-lines of Grossouvre's 

 Coniacian species are considerably simpler than are those of the Cam- 

 panian delawarense-gronp. It has been possible to develop the 

 internal portion of the suture-line of the present species, and a com- 

 parison with that of M. texanum (Burner) as figured by Schliiterj| is 

 interesting as showing not only great increase in complication, but 

 accommodation to a different whorl-shape. The suture-line of an 



* " Gast. and Ceph. of the Earitan Clays, etc.," ' Mon. U.S. Geol. Surv.,' vol. 

 xviii (1892), p. 252, pi. xliii, figs. 1, 2 only. 



t " Etudes de Pal. Tunis," I, ' Ceph. d. Ter. Second,' 1907, p. 243, pi. XL, figs. 21 

 and 22. Pervinquiere, in his note (1) on p. 244, somewhat misrepresents 

 Whitfield, for the remark in the latter author's description of M. vanuxemi 

 (p. 254) refers to the compressed specimen he figures (pi. xlii, figs. 3 and 4), 

 not to Morton's type. The latter is somewhat doubtful. It would be advisable 

 to take as type of M. delawarense, Morton sp., figs. 6 and 7 in Whitfield, and as 

 type of M . vanuxemi (Morton em. Whitfield), figs. 3 and 4 of the same plate (xlii) 

 in Whitfield. Stuart Weller (loc. cit., p. 839) unites the two species again in 

 the writer's opinion unjustly. 



t " Up. Cret. Dep. of Maryland," ' Maryland Geol. Surv. Baltimore,' 1916, 

 p 391, pi. xii, fig. 7. 



Hoplites vari, Schliiter var. mar rot i in Grossoxivre, loc. cit. (1894), p. 119, 

 pi. viii, fig. 36= Hoplitoplacenticeras, Paulcke. 



| "Cephal. d. Ob. Deutsch. Kreide," ' Palaeontogr.,' vol. xxi, part 2 (1872), 

 p. 41, pi. xii, fig. 3. 



20 



