IREDALE : NOMENCLATURE OF BRITISH MARINE MOLl.USCA. 343 



Genus Cryptodon Tuiton. 

 Thyasira Lamarck has been used on the score of priority. This 

 name was simply introduced in synonymy, but this has been con- 

 sidered acceptable under the present nomenclatural laws. 



Genus Venus Linne. 

 A criticism of Ball's and Jukes-Browne's papers would probably 

 necessitate alterations in the subgenera here admitted. The type 

 of Venus, as determined by Dall and confirmed by Jukes-Browne, 

 seems to need reconsideration in view of my data. 



Genus Tapes Megerle von Miihlfeld. 

 This should be displaced generically by Paphia Bolten, while 

 subgenera should be admitted. 



Genus Irus Oken. 

 This name has recently been replaced by Venerupis Lamarck. 



Genus Psammobia Schumacher. 

 Gari Schumacher has priority and seems coincident. I know 

 of no valid reason for tlie rejection of this name. 



(Jenus Acmaea Eschscholtz. 

 The British shells, either viewed conchologically or anatomically, 

 are not congeneric with the type of Aimaea, which moreover is 

 invalidated by a prior Aanea. Tedura should be revived. 



Genus Eumargarita Fischer. 

 Margarites Gray 1847 ^^'^s proposed as a substitute for the pre- 

 occupied Margarita Leach over thirty years prior to Fischer's 

 introduction and is now commonly in use. 



(ienus Monodonta Lamarck. 

 I would not consider the British species congeneric with the 

 Austral type of Lamarck's genus and I note that Pilsbry placed it 

 in the genus Osiliiius. 



Genus Littorina Ferussac. 

 I consider the genus here shown to be polyphyletic and would 

 restrict Liitorina to obtusata (Linne), using Melarhaphe Menke for 

 jieritoidcs (Linne) and probably some other name for the remain- 

 ing members, which I have not studied. 



Family Rissoidse. 

 'J'oo many genera seem here recognised and a careful revision 

 is necessary. I had occasion to study the Norman GoUection, now 

 in the British Museum, in an attempt to fix the generic names 

 commonly applied to Neozelanic Rissoids and came to the above 

 conclusion. 



