312 J. E. S. MOORE. 



of tlie upper cretaceous series a form which united by insensible 

 gradations the conchological characters of Melanopsis, 

 Paludomus, Pyrgulifera, Melania (amarula) and Para- 

 nielania. But if on this ground it should be maintained that 

 the living representatives of these different groups have any 

 immediate phylogenetic relationship with each other, all that 

 can be said by anyone acquainted with the morphology of such 

 of them as now exist must be that although a deduction of 

 this kind from the characters of living and extinct shells may 

 be conchologically correct, it is also at the same time morpho- 

 logically nonsense ; there is no sort of morphological similarity 

 between Melanopsis and a Melania amarula. These 

 forms, as the investigations of Bouvier have shown, should by 

 right be placed in different families. Paludomus differs 

 from them both, while the Paramelania of Tanganyika is 

 altogether unlike any of the three. Thus if the genus 

 Pyrgulifera corresponds to any of these types which now 

 exist, it differs from all the rest which I have named. If 

 Pyrgulifera humerosa was morphologically similar to 

 Melanopsis, it was not a Paramelania. If, on the other 

 hand, it was a Paramelania, it was neither a Melampus 

 paludomus nor a Melania proper. There is thus really no 

 direct reason why the Pyrgulifera of the chalk should not 

 have been a Paramelania ; but since the genus Pyrgulifera 

 has been shown by Tausch to correspond equally to three 

 widely distinct living types, it is clearly more than three to 

 one that such was not the case. 



As to the question of the identity of the entire fresh-water 

 fauna with which the Pyrguliferas are connected in the upper 

 chalk, and that consisting of the halolimnic group in Tan- 

 ganiyka, whether we regard the Paramelanias and Pyrguliferas 

 as similar or not, it will be obvious that as there are no other 

 forms in these faunas bearing the slightest resemblance to one 

 another, the question of their general identity is ipso facto 

 out of court. Not only do the halolimnic animals differ from 

 those of the fresh-water fauna individually, but the whole 

 halolimnic fauna differs entirely from the cretaceous or any 



