110 



SOLLAS On the Origin of Freshwater Faunas. 



the date of their earliest known existence appended. It will be seen that Neo- 

 thaunia is a Paludinid, and consequently a modified freshwater genus not marine. 



Tiphobia, which Mr. Smith regards as one of the most marine-looking of the 

 whole fauna, is not only a Melanian, and therefore a genuine freshwater genus, 

 but includes Paramelania as a sub-genus ; and this is closely allied to, if not 

 identical with, Pyrgulifera, which is known as a freshwater form so low down as 

 the Laramie beds of North America. Limnotrochus, which Smith speaks of as 

 exceedingly like a Trochus, both in general form and sculpture, is assigned by 

 him to the Littorinidse, a family which is already represented by one freshwater 

 genus in the lower Pliocene beds of Europe ; and since Lithoglyphus occurs 

 together with Limnotrochus in the lake, it is quite possible that both have descended 



This genus may belong to the Melaniinse. 



