The Invertebrate Fauna of the Uitenhage Series. 175 



Dimensions. 



Height of shell 27 mm. 



Height of aperture 17 ,, 



Greatest width of aperture 10 ,, 



Occurrence. Collected from the cliff on Buck Kraal, Sunday's 

 Kiver (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 Eiver. 



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. Eehbinder 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), pi. xxxviii., fig. 13 ; see also Zekeli (1), p. 45, 

 Taf. viii., fig. 2. 



t Zekeli (1), p. 46, Taf. viii., fig. 4. 



J Rehbinder (1), p. 139, pi. ii., figs. 12, 13. 



