during the fifth whorl. At the middle zone, and below, the whorl is evenly convex in outline. The shell-wall is thick. The surface of the whorls is marked by numerous distinct, transverse growth-lines, which, however, do not form an obtrusive feature. The spiral angle is about 90°. The inner lip of the aperture is considerably thickened and forms a raised callus which bounds a well-impressed though closed umbilical slit. Just below this, and adjacent to the inner lip, the surface of the whorl presents a narrow, slightly flattened space. The height of the aperture is much greater than the breadth. Dimensions.— Height of shell (1) 15 (2) 8 24 12 "" Height of body-whorl at the aperture 11 Greatest width at aperture Occurrence.-Two well-preserved specimens in the collection of the Geological Society of London are labelled "Zwartkop, Dr. Atherstone, 1876." A specimen from the railway cutting between milestones 24-243 on the railway from Uitenhage to Graaff-Reinet, about three miles from Uitenhage (350), is referred with some doubt to the same species. Remarks.-The specimen from the railway cutting (350) may perhaps be identical with Atherstone's two individuals, upon which this species is founded. It differs from them by its rather lower spire and slightly wider spiral angle, and by the more complete overlapping of the whorls. These differences may, however, be due to individual variation. Natica atherstoni Sharpe, another Uitenhage shell, is distinguished by its much more slender and elongated figure and narrow apical angle (75°). Compared at similar dimensions, Natica lævigata (Desh.) Leym.,† a Lower Cretaceous form, has much less overlap of the whorls, and consequently a higher spire and narrower spiral angle. N. dupini (Desh.) Leym.,‡ on the other hand, has a shorter spire and wider spiral angle, with wider and more inflated whorls and less elongated mouth aperture. The shell figured by d'Orbigny as N. dupini § shows much greater similarity to N. uitenhagensis, but this too has a wider spiral angle and a broader aperture as well as a distinct umbilical opening. In form and outline and in the shape of the aperture great resemblance is shown to the shell from the Stramberg beds figured by Zittel as Natica (Ampullina) elegans Sow.; this differs, however, by the slightly less overlap of the whorls and by the thinner shell; the inner lip is considerably less thickened than in the African form. It seems doubtful whether the Stramberg shell is identical with the English Portland Natica to which Sowerby gave the name N. elegans, and although Sowerby's figure † much resembles fig. 23a in plate 45 of Zittel's work, yet typical specimens of the Portland shell show a higher spire. Natica uitenhagensis is well distinguished from the English N. elegans by the much thicker shell and the lower spire. The shells from the "Portlandien supérieur" of Boulogne, ascribed to Natica elegans Sow. by de Loriol and Pellat, whose determination was accepted by Hudleston and Wilson, § are also slightly higher in the spire, and the aperture is broader and more rounded below. The form described by Stanton as Lunatia constricta, from the Belgrano beds of Patagonia, shows great similarity to N. uitenhagensis, but differs apparently by the more strongly impressed sutures, the slightly less overlap of the whorls, and by the marked transverse furrows. NATICA ROGERSI sp. nov. Plate VIII., figs. 12, 12a, 13, 13a. Description. The shell is small, and consists of four whorls in the specimens examined. The body-whorl overlaps a little less than one-half of the preceding whorl, and occupies about two-thirds of the whole height of the shell. The spiral suture is well impressed or slightly channelled. The whorl-surface traced downwards from the suture presents an evenly convex surface. The shell-wall is rather thick. The surface is marked by numerous transverse lines of growth and there is also a tendency to produce coarser, rounded, transverse ridges and furrows. The spiral angle is about 90°. The mouth aperture is broadly rounded below and narrowed and somewhat pointed above. The height of the aperture does not greatly exceed the breadth. The outer lip is sharp. Below, the margin of the aperture is thickened. On the inner side * Zittel (4), p. 289, Taf. 45, fig. 23. J. de C. Sowerby (2), p. 347, pl. xxiii., fig. 3. § Hudleston and Wilson (1), p. 81. || Stanton (3), p. 31, pl. vi., figs. 10, 11. Occurrence. Found by Mr. Rogers in the cliff on Buck Kraal, Sunday's River (136h). Remarks.-This form is distinguished from small specimens of Natica uitenhagensis sp. nov. by the rather more expanded and less elevated figure of the shell, and the broader and more rounded form of the aperture. A specimen from the neighbourhood of Uitenhage (350), ascribed above with some doubt to N. uitenhagensis, is comparable in point of size with individuals of N. rogersi. It differs from these by its broader apical angle, shorter spire, narrower and more elevated figure, and relatively higher body-whorl and aperture. NATICA? MIRIFICA sp. nov. Plate VIII., figs. 14, 14a. Description. The shell consists of at least six whorls, and has a somewhat elongated turbinate outline with the body-whorl well produced and narrowed below. The body-whorl overlaps about half the preceding whorl, and occupies rather less than two-thirds of the total height of the shell. The spiral suture is well impressed, and below it the whorl-surface bulges out in the form of a convex spiral fold. Immediately below this rounded swelling of the whorl-surface is a depression of the surface forming a concave spiral band. This impressed zone is less well developed in the earlier whorls, more pronounced in character in the later ones. At the middle zone of the whorl the surface is again convex, and below this the whorlsurface slopes inwards with less marked convexity. The concave and convex zones in the upper half of the whorl merge into one another without the production of any angularities of the surface or of the outer lip of the aperture. The shell-wall is moderately thick. The surface is smooth and only marked by transverse growth-lines. The spiral angle is about 70°. The aperture is elongated, its height being about twice as great as its maximum breadth. It is angular at its upper extremity and has a narrowed, rounded outline below. The inner lip is thickened and a callus is developed. There is a short, narrow, but closed umbilical slit. Dimensions. Height of shell Height of aperture Greatest width of aperture 27 mm. 17 10 Occurrence.-Collected from the cliff on Buck Kraal, Sunday's River (137h). A fragment of a specimen, probably belonging to the same form, was obtained from the cliff W. 20 S. from Comley's house, right bank of Sunday's River. Remarks. This is a rather peculiar shell, and I am unable to state with certainty its true generic position. In spite of the elongated form, the relatively narrow spiral angle, the narrowed aperture, and the body-whorl produced and narrowed below, the characters of the shell appear on the whole to conform with those of naticoid type, while the close and smooth texture and lustrous appearance of the surface, when well preserved, seem to favour alliance with some division of the Natica. A striking feature of the shell is the longitudinal (spiral) depression of the surface of the whorls in their upper part. This character in less emphasised form is not unknown in Natica, though I am not aware that any described species exhibits it in such a marked degree as in the shells under discussion. The well-known Natica bulbiformis from the Gosau beds, figured by J. de C. Sowerby,* has a distinct depression of the surface corresponding in position with the stronger sulcation in this African form. N. bulbiformis also has a relatively tall spire, but it is otherwise well distinguished by its more cylindrical whorls, the deep channelling at the suture and the more oblique direction of the mouth in relation to the long axis of the shell. Natica angulata from the same beds, † first figured by Sowerby, also shows in some degree a corresponding depression in the surface of the whorls. There is a very close resemblance between Natica? mirifica and a Cretaceous gasteropod from the steppes of Astrakhan, described and figured by B. Rehbinder under the generic name Odostomopsis.‡ The general form of the shell and the undulating outline of the whorl-surface is strikingly similar, but generic identity seems excluded by the absence of any fold on the columella in the African form. It may be questioned whether the specimens depicted in Rehbinder's figures 12 and 13 are identical with the originals of any of the other figures given by him under the same * In Sedgwick and Murchison (1), pl. xxxviii., fig. 13; see also Zekeli (1), p. 45, Taf. viii., fig. 2. † Zekeli (1), p. 46, Taf. viii., fig. 4. Rehbinder (1), p. 139, pl. ii., figs. 12, 13. specific name, and it is very doubtful whether they are correctly referred to Odostomopsis abeihensis (Blanck.), but it is certain that the Uitenhage form here ascribed with doubt to Natica cannot be brought into close comparison with Whitfield's genus.* GENUS ACTEONINA A. d'Orbigny. ACTEONINA ATHERSTONI (Sharpe). Plate VIII., figs. 15, 15a, 16, 16a, 16b. 1856. Acteon atherstoni D. Sharpe, Trans. Geol. Soc. Lond., ser. 2, vol. vii., p. 200, pl. xxviii., fig. 19. Supplementary Descriptive Note.-The shell consists of about six whorls, in the last of which there is a tendency to develop a steeply sloping and slightly convex shoulder below the suture, demarcated from the flattened central portion of the whorl by an ill-defined, blunt spiral ridge. The previous whorl also shows these characters, though in less marked degree, but the earlier-formed whorls have a more evenly rounded outline, most convex near the suture, more flattened below. The whorls are ornamented over their whole surface by numerous delicate, impressed, linear, spiral striæ which are crossed by more conspicuous furrows and rounded ridges of accretion, most noticeable in the last whorl. The spiral angle 4.5,, Greatest width of the aperture................ Occurrence.-Collected at Grass Ridge, three miles east-north-east of Uitenhage (333), and from a clay-pit in the lower part of the Marine Beds on the left bank of the Zwartkop's River near Rawson Bridge (343); also at Dunbrodie, Sunday's River (283, 284). Specimens from the South African Museum are from the Sunday's River. The record of occurrence given by Sharpe was "the lowest strata of the Zwartkop crag." Mr. Rogers collected specimens of this form in 1905 at the bare slope W. 30 S. from the middle of Barkly Bridge, on the farm Olifant's Kop, Sunday's River (24h); from the highest beds in a kloof behind Colchester, Sunday's River (499g); and from a cliff W. 20 S. from Comley's house, right bank of Sunday's River (92h). From this last locality was also obtained a specimen (95h) * Whitfield (1), p. 425. |