Notes on South African Mollusca. 173 



variable one. Little reliance can be placed on the comparative size 

 of the shell, height of the spire, or shape of the aperture, but the 

 perforation varies from a slit to a well, and the sculpture from fine 

 and regular to irregular and costate. Moreover, the difference in 

 anatomy between the only two forms which have yet been examined 

 may well be more than merely varietal. It is quite possible, there- 

 fore, that, when we have a better knowledge of their anatomy and 

 exact distribution, more than one of the so-called varieties of 

 alexandri will be proved worthy of specific rank. On the other 

 hand, it will be seen that the gradual, constant divergence from 

 Type increases quite regularly in a northerly direction, from the 

 rimate typical form with hardly visible sculpture in the south, 

 through rotundata and trivia, to the widely umbilicate perspective!, 

 with costate sculpture in the north. This gradual divergence is 

 less incompatible with all the forms belonging to one species than 

 if they were scattered about indiscriminately, irrespective of 

 geographical restrictions. I therefore prefer, for the present, not to 

 disturb the varietal arrangement ; it can easily be done later, if 

 wan'anted by the occasion. 



GENUS TULBAGHINIA, Melv. & Pons., 1898. 

 A.M.N.H. i. p. 28. 



Shell rather large, depressed-globose, umbilicate, usually cor- 

 neous and ornamented with bands or mottling ; peristome thickened 

 or reflexed, sometimes showing weak dentition on the colurnella. 



Animal unknown. 



Distribution. The South-western district of the Cape Province, 

 chiefly in the more wooded areas between Tulbagh and Bredasdorp. 



Genotype, Tulbaghinia isomcrioidcs (M. & P.). 



Founded as a sub-genus of Dorcasia for T. isomerioides, on 

 account of its peculiar columellar formation. As it is extremely 

 doubtful whether this species belongs to the Dorcasiinae at all, it is 

 obviously advisable to raise Tulbaghinia to generic rank. I have 

 no hesitation in including schaerfiae, Pfr., in the genus on account 

 of its close conchological affinity with the genotype. 



The general appearance of the shell, especially the white, thickened 

 peristome, recalls certain members of the Dorcasiinae, and, until 

 more is known of the animal, I am content to regard the genus as 

 representing the sylvan races of the subfamily. 



