168 Annals of the South African Museum. 



Dimensions. 



Height of specimen with five whorls ... 11 mm. 

 Diameter of the fifth whorl 7 ,, 



Occurrence. In the cliff below the old school-house at Dunbrodie, 

 on the right bank of Sunday's Eiver (282). 



Remarks. This shell, represented in the collection by only two 

 specimens, appears to be so closely related to Turbo atherstoni that 

 at first I felt some hesitation in definitely separating it. A careful 

 comparison with the specimens of T. atJterstoni from Dunbrodie and 

 those in the museum of the Geological Society shows, however, that 

 it possesses distinctive characters which appear in no specimen of 

 T. atherstoni that I have examined ; the points of difference are as 

 follows. In T. atherstoni the upper and lower marginal keels are 

 very prominent and the outer area of the whorl concave in profile ; 

 the marginal keels in T. rogersi are less pronounced and the outer 

 truncated area flat and vertical in profile in the earlier whorls. The 

 central keel of T. rogersi makes its appearance much earlier and 

 gains in strength so that it rapidly becomes as prominent as the two 

 original peripheral keels ; this equality is not attained in T. ather- 

 stoni. In T. rogersi two additional raised ornamenting lines appear 

 on the peripheral area, while larger specimens of T. atherstoni, illus- 

 trating a more advanced stage of growth, have shown no similar 

 development. Another feature of distinction is seen in the manner 

 in which the whorls of T. rogersi lose their angularity of form with 

 advancing growth and present an even convexity of surface not seen 

 in the largest specimens of T. atherstoni. It is impossible to speak 

 with certainty of any differences in the spiral angle, but the com- 

 parison of additional specimens, when these are forthcoming, may 

 possibly show that the angle of T. rogersi rather exceeds that of 

 T. atherstoni. 



A Turbo described by Zittel from the Stramberg beds under the name 

 Turbo eryx d'Orb., var. major'''- is of similar type to T. rogersi, but 

 differs in the more expanded form and wider spiral angle, and in the 

 details of the spiral linear ornaments. 



TURBO MINUTULUS sp. nov. 

 Plate VIII., figs. 9, 9a, 9b. 



Description. The shell consists of at least four whorls, and these 

 are flattened above and sloping gently away from the suture, but 

 vertically truncated at the periphery. The truncated marginal band 



* Zittel (4), p. 321, pi. xlviii., fig. 10. 



