80 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



two forms are known to be anatomically distinct, and therefore it 

 becomes certain that they cannot both be the same as Purpurina. 

 However, as I have above observed, I consider Nassopsis { — Lavigeria) 

 distinct. 



3. Bathanalia Howesi and Amberleta. 



These two forms are very similar in general outline, but differ in 

 the former being umbilicated, and having a thin continuous peristome. 

 Amherleya is imperforate, and the columellar margin of the peristome 

 is tbickened and re flexed. I may mention that Mr. Moore's figures 

 of Bathanalia both in the Quarterly Journal of Microscopical Science 

 and in " The Tanganyika Problem" have this margin of the aperture 

 reflexed in an exaggerated manner, so that it does somewhat resemble 

 that oi .Amherleya. I do not propose to assert that the fact of 

 Bathanalia being umbilicated distinguishes it generically from 

 Amherleya, but merely point it out as a feature which, in conjunction 

 with the other difference referred to, seems to indicate that these 

 ancient and recent forms are not the same. Something more than 

 a mere general resemblance is wanted before we can say that such 

 genera as these are identical. I may add, however, that if we knew 

 that the animals of the shells in question were similar, there would 

 be no attempt to part these forms on conchological grounds, but as 

 we have not this knowledge it seems to me very hazardous to unite 

 them, more especially considering the countless ages which have 

 passed since Jurassic times. 



4. LiMNOTRocHus Thomsoni and Littorina sulcata. 



In this case also the Tanganyikan shell is umbilicated and the 

 Littorina imperforate, but the columellar margin of the peristome in 

 the Limnotrochus is less reflexed and the whorls are spirally ridged, 

 and without the longitudinal plicge which are found in the Littorina 

 referred to. Here, again, the shells do not offer any very striking 

 differences, but still 1 should hesitate to unite them, as they do not 

 absolutely agree in all respects. 



5. Chttea Kirkii and ONtrsTtrs. 



The form of Oolitic Oniistm with which Mr. Moore compares 

 the Tanganyikan shell is radiately costate, whereas Chytra exhibits 

 only spiral ornamentation. The peristome is not continuous, as in 

 the latter form, nor is the lower margin of it deeply sinuated in the 

 same manner. In one feature Chytra Kirkii differs entirely from 

 Onustus (or Xenophora), namely, in the character of the operculum. 

 In this respect it approaches certain forms of Littorinidae, e.g. Pagodus 

 and Echinella. 



6. Spekia zonata and Neridomtjs. 



In this instance, Mr. Moore observes that "the shells of the 

 Tanganyika genus Spekia are practically indistinguishable from the 

 fossil remains of the shells of the marine Jurassic genus Neridomus^ 

 This, in my opinion, is entirely wrong, as the character of the base 



